OdorXit.com has a water and essential oils solution that as long as you get it to ALL the urine - drywall, concrete, the 2x4's behind the drywall, even the duct work, it will eliminate the smell 100%. 

We had heat pumps with duct work north of Toronto Canada.

You could leave the asbestos in-place until such time as it is convenient for you to remove it, provided it remains undisturbed and there is no path by which friable asbestos can enter the living area {essentially a good vapour barrier around all fixtures and properly sealed ductwork if it passes through the attic}.   

So you'd need to add that in with the cost of doing the work, including running duct work.

, foundation (a few cracks in drywall in master bedroom) and possibly duct work (all registers have been removed and there are cobwebs and junk visible ( may just be part of winterizing?

Considering easy access with crawlspace below, and as long as there isnt a bunch of ductwork or plumbing in the way, this is quick, easy, and cheap.As long as the planking is sound, there shouldnt be much give between joists.

I have a unit where they placed the forced air furnace and duct work for the 2nd floor in the attic, and pulled the power and gas supply through the chimney.  

You might have to replace the flooring, clean the ductwork, seal the walls with shulac or Kilz etc....  

I've heard of the typical stuff (copper piping and wiring, ductwork, etc)...

One rental I had melted crayons in the light fixtures in the ceiling and in the duct work and they removed the wall paper.