Having given up on ever getting the old fan motor out, and using the rationalization listed in a previous post (old things wear out), I've decided to go ahead and replace the whole furnace. My question therefore becomes - are there "sub-models" so to speak, of the Atwood 8940-III DCLP? In other words, will a new one just "bolt" right in or are there problems like the propane hookup possibly being different?