Very sweet little "egg" you have there, and in such good condition! I especially like the windows, you don't see sliding windows installed in vintage trailers that often.
When you reseal the roof, make sure that you install either Eternabond tape after cleaning to "hospital sanitation" or use one of the good sealants--Dicor or Geocel product, then the roof coating can follow. It looks like your problem area on the roof may be around the vent opening but it is good practice to seal all the joints up there.
Good luck with your little egg!