The good news is that nothing that you list is much more than normal maintenance. Replacing the propane gear is obviously the highest priority and should be done using only marine parts. As for price, you can get good quotes from any online site. I'd suggest using westmarine.com. Their prices will be the highest but that will give you some bargaining room. Unless you're handy, you should have the work done by a competent yard. Assume about $70/hr. Basically, think each repair through and estimate how long it would take you to do a first class job (in hours). Then double it and multiply by $70. Add in the cost of materials and double that too. Subtract the combined costs from your original bid and then reduce it 10% more. As a cross check, get sample vaues from yachcouncil.com, boatus.com or any number of online sites for a similar Catalina. Even though the asking prices are higher than the sell prices, you'll get a good idea of the market value of the boat. Since the surveyor looks at LOTS of boats I'd take his advice seriously.
Good luck! Your surveyor's list is not bad....you should have seen mine - it went for pages, but I'm glad that we bought "Victoria" and she's (now) an awesome boat.
Sabre 38 "Victoria"