Michael ,I would start by sealing your roof with the appropriate primmer and coating(exterior).Is yours a rubber roof like mine.? Then scrape all the brown paper off with a razor blade scraper get as much off as you possibly can. Let me back up a little bit. Start by removing the cupboards and covering all floors and tops of stationary furniture with cardboard and duct tape. Get a roll of heavier plastic to cover your couches. After you have stripped all walls of the brown paper you will coat the inside of the fiberglass with 3m bondo. Possibly something at Walmart is the equivelent. Do an internet search. If you are not sure if you have to strip the end walls remove windows. You will have to remove every window in the trailer and reseal with butyl tape and seal with lexell caulk. With the windows removed you can see the condotion of the layers of the wall. If you have delamination and water dammage. I have explained in my posts how to remove windows and reseal. Everyone with windows ten yrs. old should do this. Don't wait until the windows leak before resealing. Then it is often too late as you have wall dammage. Some of your windows will require you to wrap the butyl tape around twice to fit the wavy fiberglass. Now to answer your questions about replacing the insulation. You do not need fire proof insulation. You can go two ways with this. Check out the old posts for a tank of icene blow in insulation. I wanted to rip all our walls out except the ends. DH only ripped two walls completely out.Why are/were our trailers in such leaking poor condition? We looked many times at the exterior caulk and thought it was alright,maybe we just put more on top. Should have scraped it all off and applied Lexell caulk. The fiberglass aged and develops minute pin holes that you can't see thus the need for bondo to seal it up. Big area of leakage is the escape window at the dinette. we took out the window and used foam weather strip to reseal and lexell caulk. We also used foam spray insulation in a can/frustrating because some goes to waste if you can't use it up quick enough. Another area of leakage was the outside and inside AC outlet box. Got a new box from our HiLo dealer.Another area of leakage was the outside light assembly. Several times we were glad it rained when we had the wall torn out and had finished repairs as we could see a few drops of rain on the inside and had to do a little bit more caulking. You can use sheets of insulation on your walls. Since you have so many walls torn out I would get a thin roll of water proof vapor barrier at home depot to replace the brown paper. Probably the staining you see in the BR ceiling could have come from the leaky vent in the middle of the room. My biggest concern for you is the exterior and interior condition of your roof. Our roof is maxed out after 21 yrs. We had a good rain Sunday for the 1st time all summer and I will have to get over where we park our HiLo and check our extensive patch job. I am sure the exterior roof is delaminated in spots and we have and exterior ares where the glue let loose/wrinkling. Some wrinkles over the patched area on the inside. Didn't realize our roof was going bad when we start our demolition. Might have been discouraged and wouldn't have wanted to do all that work. Keep in mind that if you could buy this trailer new it would probably cost $ thirty five thousand. So maybe $2,000.00 in materials with a roof rebuild and extensive renovation. Keep us posted.

Any rusty metal that you come across must be treated with rustoleum metal primmer and rustoleum paint. Maybe even treat all metal even if in good condition as this what JR repair does. Good ahead and beef up any areas in the wall with additional metal or wood strips in the foam. Especially where the awning attaches. We popriveted into the metal studs where necessary for extra strength. Use blue tape to mark off where your roof coating will stop where the roof goes down over the side.

I think the roof is rubber not metal when I removed the roof panel in the bathroom i could see what looked liked wood looking plastic barrier. I am getting the money together to buy the material to get the roof stuff and the tape and caulking. I do not know if I will get it done before Xmas but i can hope.
will tell you more when i can type more.
Michael

Spoke with my husband today about the advice I gave you. He said the Bondo we bought is a two part epoxy by 3M. It goes on as a liquid and dries hard. I think I remember seeing this at Auto Zone. You should be able to get this at some of your local auto stores. We probably paid a few dollars more because we bought it at a local supplier to colission shops. Worth every penny to seal the fiberglass against leaks. We used about 1/2 can for two panels of fiberglass.

Collision,tired long day.