I agree with DrewE on both counts.
Also, it hasn't been brought up, but make sure to do a full test on the fuel lines and propane system. Those old fuel lines deteriorate and get pinholes in them. I had 15ft of line replaced - they couldn't find any leaks in the lines because smoke was coming out the entire length.
Check the propane system all the way through. I had a leak inside the heater line. Even though I wasn't going to use the heater, that leak was coming into the RV every time I turned on the propane. I ended up shutting off the heater connection and now all is good.
