Getting rid of carpet and repainting will help, but you will also need to have the duct work cleaned.

Just putting in central AC in my market is 16k ( 8k for the AC/duct work, 8k for the electrical updated to support the AC).

Installed gas water heater, new gas fed HVAC system, ran ductwork for returns to allow for A/C.

That could be electrical, plumbing, and even ductwork.

Most of it was no big deal, but we did have to open up some walls and ceilings so that they could make sure electrical was in conduit, fire blocking was in place, duct work was correct, etc.

Fire damage--remove and replace; smoke damage--clean and deodorize (keep in mind that pretty much everything in the same airspace will have some measure of smoke contamination--this even includes the HVAC ductwork) ; water damage--mitigate and dry out (but if its remained wet for a period of time you might be looking at mold--remove and replace).

You can try Roofing.QualitySmith.com i found this with a quick search they offer an on line bidding system. you should ask the roofers if there insured, there experience in roofing, for some referrals also make sure to get several bids. a job like a roof has a lot of labor cost in it so bids will vary. id also get bids on the job with a tear off and an overlay. if your replacing the air cooler then the installer of the new unit should disconnect and remove it properly. roofers might brutally remove it and destroy mounts,connections or duct work and make more repairs for you. plus they may throw it off the roof Ive seen it done.

. $3000HVAC: new furnace, ductwork as nec, AC

It all depends on your setup and current duct work. 

This is a good choice especially for a non-forced air heating system.But as for putting in a central A/C unit, if you already have a Nat Gas furnace, the duct work is already there, all you have to worry about is some degenerate steeling the coolant and breathing it to get "Far Out".I mention that because the newer type coolants (required by law) are very expensive to replace.Good Luck!