John, replacement lenses are not available. Someone was working on reproducing them but I think gave it up.
Windows are typically leakers, but they can be rebuilt. Better yet another owner found a source for replacement "clamp ring" type
windows that are reasonably priced. The front and rear
windows are clamp ring type whereas the side windows use a rubber weatherstrip to hold them in. You can find some good info here in the document center and there is now a very active
Uhaul facebook group. Over there we set up a "common issues" and info file for new owners. Check it out. Where in NC are you. Another thought on the
tail lights, I've seen a couple Uhauls where the area was fiberglassed in resulting in the same curve and new
lights either surface mounted or flush mounted. Wiring is odd in these trailers unless it has been redone.