Doug, I would recommend that you start from the outside and work your way in. The first thing to check would be the axle
and suspension for any parts that need replacing. While you're under there, do a thorough check of the frame. Assuming all is well, then check all windows
and extrusions. If they are glopped over with Silicon, then you will probably want to remove and reseal them properly. If you remove the windows
, consider replacing all the rubber parts if they are original or hardened and damaged. Assuming you are going to repaint the trailer, removing all the windows
and extrusions would be best before painting
. Once the outside is buttoned up and good, then you can start on the inside.