You will find wood wall & ceiling framing in many older units, aluminum in the later ones.
As of late, the preferred flat sheet flexible fiberglass has become more popular for roofing. Higher maintenance rubber and TPO roofing was more popular in years past.
The "spark plug popping-out" issue in the Fords was resolved mid production in 2003. 2002s surely have the problem. 2004s surely don't.
Fuel economy will be noticeably worse in Fords prior to 1997, and the GM/Chevys prior to 1996. If you go way back when carburetors were used, your fuel economy worse yet, and performance greatly reduced. I think carbs dropped out around 30 years ago.
You will get something extra good if buying a brand new motor home built on a 2017 Ford chassis. The new 2017 Ford E350 and E450 are getting a brand new transmission with one more gear for a total of 6 for improved fuel economy and driving behavior.
