I'm sorry, but I don't know of any type of grass that tolerates dog urine well.  Fescue lawns are less sensitive than Kentucky bluegrass, but they still get damage.  Some people try to train their dog to go in one area of the yard.  Watering the area where the dog goes within a few hours can help minimize damage by diluting the urine.  This is a very common problem that lots of us just learn to accept because we love our dog!

   Because there is an aspen tree in the lawn you will need to provide additional water and fertilizer for the lawn.  If the lawn has a fungus you will see symptoms such as dead areas with green grass in the center or serpentine dead areas.  There are lawn fungicides available to spray on the turf.  Look for them in the garden section of Lowe's and Home Depot or at garden centers.

   It is too soon to apply weed killer to a recently seeded new lawn.  You should not apply a weed killer until the lawn has been mowed 4 or 5 times.  At that time you can use a weed killer for broadleaf weeds in turf.  Once the lawn is established you can use pre-emergent weed killers that prevent weeds from growing.

   Which grass is the best depends on a number of factors.  Please see http://www.csuturf.colostate.edu/.  Click on "Home Lawn Care."  Click on "What is the best grass to plant in my new lawn?"  This link will take you to a list of several helpful articles on this topic.

   Yes, you can lay sod this time of year in Colorado.  Be sure to water it once or twice a month in winter when the ground isn't frozen. 

   The following is information on power raking from CSU Cooperative Extension.  Core aeration is now the preferred method for controlling thatch.

"Power Raking
This method of thatch removal has been used for years. Light (shallow) power raking may be beneficial if done often. Deep power raking of a thatchy lawn can be damaging, and often removes a substantial portion of the living turf. Used properly, power raking of wet, matted turf can speed spring green-up by letting air move into the root zone and warm the turf.  Compost the thatch and organic material to kill any living grass before it's used as a mulch or soil amendment.
Core Cultivation or Aerating
This is more beneficial than power raking. It helps improve the root zone by relieving soil compaction while controlling thatch accumulation. Soil compaction, in fact, is one factor that contributes to thatch buildup.

Aeration removes plugs of thatch and soil 2 to 3 inches long (the longer, the better) and deposits them on the lawn. A single aeration using a machine with 1/2-inch diameter tines removes about 10 percent of the thatch if enough passes are made to achieve an average 2-inch spacing between holes.

Disposing of the cores is a matter of personal choice. From a cultural perspective, there may be an advantage to allowing the cores to disintegrate and filter back down into the lawn. Mingling soil and thatch may hasten the natural decomposition of the thatch. The little fluffs of thatch and turf that remain can be collected and composted.

Depending on soil type, core disintegration may take a few days to several weeks. Irrigation helps wash the soil from the cores. Dragging a piece of cyclone fence or an old metal door mat can speed the process. Running over the cores with a rotary mower can be effective but can dull the blade. Many commercial companies that perform core cultivation break up the cores with a power rake. If the cores are removed from the lawn, compost them before using them as a mulch or soil amendment."

   From your description it sounds like the lawn has a disease, possibly Dollar Spot Disease.  For information on this please see www.ext.colostate.edu/pubs/garden/02933.html.  The spiders are not related to this problem.  Mushrooms appear due to decaying organic matter in the soil.

   Colorado State University Turf Program has an informative website that can help you select the best types of turf for your property.  A low maintenance grass like crested wheatgrass would be good for outer areas.  If water is a concern, you may want to consider buffalograss.  (It is green only in warm weather.)  Close to the house you probably want a more formal type of lawn such as bluegrass or fescue.  The website lists the advantages and disadvantages of these and has lists of recommended varieties.

    To visit the site go to http://csuturf.colostate.edu and click on "Home Lawn Care."  Click on the middle box that says, "For information on starting a new lawn...."  Click on "Seeding a New Lawn."  Click on "Best Species and Varieties." 

   Mushroom fungi commonly live in the soil and thatch layer of lawns.  If you have rings of lush green grass with mushrooms growing in the ring bands, the condition is called fairy ring.  The fungi can create dead patches by building up a mycelial layer that prevents water from seeping through to the grass roots.

    To control mushrooms or fairy ring in turf you should water regularly, follow fertilization recommendations for blue grass lawns, and core aerate the lawn in spring and fall.  If water tends to run off, you may want to apply a wetting agent such as Revive.  A fungicide can be applied, but it will have only a limited effect.

   The most drought resistant lawn would be Buffalograss.  However, it doesn't do well in shade and doesn't tolerate traffic from pets very well.  Turf-type tall fescue is drought resistant when the soil permits deep rooting.  It tolerates traffic well.  A blend gives better results than use of a single variety.

    For information on reseeding a lawn please visit http://csuturf.colostate.edu.  Click on "Home Lawn Care."  Click on "Renovating an Existing Lawn."  Also, you might want to click on "Colorado seed companies" at the bottom of "Seeding a New Lawn" for a list of sources for quality seed.  These companies can make helpful recommendations.

  While seeding a lawn should be done by mid to late September, you can sod a lawn through late fall.  You would be wise to do it as soon as possible so the roots are well established before the ground freezes.  Because the sod will not be deeply rooted, you should continue to water the sod during fall, winter and early spring when the temperature is above freezing and the ground isn't frozen.  Try to water once or twice a month during this period.

  I believe you can plant crocus bulbs under bluegrass blend turf, although crocus bulbs are more commonly planted in buffalograss.  The bulbs should have no problem sprouting up through a new bluegrass lawn because a new lawn doesn't have a build-up of thatch yet.  Be sure to amend your soil before planting.  Bulbs require good drainage or they'll rot. 

   Several types of weed killers for lawns are available.  Some kill only broadleaf weeds, such as dandelions.  Others kill only grassy weeds, such as crabgrass.  A third type kills both broadleaf and selected grassy weeds.  It sounds like this is the type you need.  Bayer Advanced Lawn All-in-One Weed Killer for Lawns is an example of a product formulated to kill both types of weeds.  Round-up is an example of a fourth type of weed killer.  It is non-selective, which means it would kill both the bluegrass as well as the weeds.

    The time you need to wait between spraying for weeds and overseeding the lawn depends on the product you use.  Therefore, you should be sure to check the label.  The Bayer Advanced Lawn Weed Killer requires that you wait 3 to 4 weeks.  This period will be longer if you have to do a repeat application of weed killer.

    The best time to seed a bluegrass lawn is late August to late September.  If you wait until spring, April or early May would be a good time to overseed.

    Grass seed is available at garden centers and home improvement stores (Lowe's, Home Depot).  Also, there are seed companies that sell it.