Thanks for the info.
After looking at it some more, I have a little damage (not from water) on all the walls. Places where curtain brackets and some spots where the wallpaper has begun to come loose from the wall board. Plus being an 88 model it's a bit dated. I believe I will tackle a major overhaul project and replace it all. But after tearing out the bad piece, I have discovered a few things. First, I don't have fiberglass. All the insulation is styrofoam blocks. Also, it appears that the wallboard was attached with screws to a square steel tube frame and then wallpapered to cover the wallboard and screws so the screw heads were not visible. So I am thinking of doing all new 1/8" fiberboard (like the stuff pegboard is made from), countersink the screw holes so the screws go flush with the wallboard, and then wallpaper over all of it with a washable, up to date wallpaper.
As for windows, I would like to take them all out and reseal them. But I would like to go a step further and actually refurbish the windows themselves as I have found one that is leaking around the seals. I need to replace the plastic pieces that hold the panes in as some of them have shrunk over the years and also the fuzzy stuff that seals between the sliding sashes of the window. The water is actually coming in so fast during a heavy rain that it is pooling in the lower window channel and splashing up and over the lower section of the trailer and getting the sofa wet. It's not a problem when the trailer is lowered. Hasnt done any wall damage cause it just leaks onto the ground. But a major problem when in the up position. So I have a bit of work to do to make this trailer right.