When I renovated our 92 I took the inside paneling off from the inside, made measurements, diagrams etc of all the framing and then made a replacement frame that included new, painted, interior paneling, new electrical, insulation, vapor barrier on the inside and and Tyvek wrap on the outside. Then in one day I took the window out, took all the aluminum siding off, removed the old panel, bolted on the new one, cleaned up the wiring, stapled the siding back onto the new wall, cut out the window opening and installed the window into the new hole.
I replaced the entire front wall from trailer frame to roof plate and the full width of the trailer in one day. (they probably built the whole thing in a few hours).
The panels are pre-built in four foot sections and assembled quickly on the line. The inside paneling is already on them so it extends below the floor and out to the edges of the trailer on the four corners. Remember that or you'll be out 1/4" and the siding won't fit back on right.
From the inside it's easy to see how it was built, don't try to repair it, if the framing is damaged or rotten then build a new panel somewhere dry and then swap it out. The siding is easy to get off so unlike modern trailers with all the spray foam the older units are easy to fix.