Hi bobkatbry. Your vintage Trade Wind has a good case of southern exposure. The rain and humidity, and maybe sea breezes, will oxidize exposed aluminum pretty good. Arizona trailers don't have this as much. It appears your trailer has a pretty good body, no major dents or holes. That is worth a bunch.
My old Trade Wind was pretty bad too. I did find my pressure washer blasted some of the crud off. But pressure washing does drive moisture into areas where it shouldn't be. Mine dried out with no lasting damage.
I think restoring the exterior skins is one of the last things on a vintage trailer renovation. That moist environment may have caused subfloor and frame rot, which should be addressed first in my view. Possibly the axles and brakes need attention too. Then move on to plumbing and wiring. Then on appliances and interior renovation. Now you have a trailer that is sound and ready for the road. You can renovate the exterior at that time.