RV Repair: RV siding replacment, pickup camper, ithink

Question
I bought a used 35' motor home about 5 yrs ago.  I have worked on campers before and built a pickup camper from nothing with out plans.  The roof needs replaced and from the roof leaking the out side is bulging, I took some of the trim off and the screws are all rusted out, I cut a piece of siding out and the under layment underneath is also wet. My question is do I remove all the siding or just in the areas where the bulging is?  I know I need to replace the wood against the siding and the wall joists if the wood is completely rotted out.  The other question I have is how do I replace the fiberglass and where do I get it?
Thanks for the help
Rich

Answer
ok  dont know what part of the county your in but you can order filon or fiberglass from mac @1-800-234-2401 it is expensive. the apr that is bulging you need to peal back and let dry if you can save the glass then you can reuse it the roof if its rubber then you can order it from trailer parts @316-262-3701 and the roof glue. The under layment is luawn or 1/8 in door skin on the side and the roof frpace the undrelayment with what ever you take off if you glue to foam us 30-nf made by 3m grainger is a good source. the wood to fiberglass glue  is 1357 made by 3m alot of this stuff is gonna hurt the pocket. If your careful you can reuse the fiber glass Ithink that is it if you need more info please reply and Ill try to get more info to you sorry about all the bad spelling its just really busy here to day good luck