congrats on the new to you tailer!
You will find everything you need and at resonable prices at the Scamptrailers.com parts store.
You can buy a bag of caps that fit every size of rivet on the trailer. They just snap onto the plastic rings around the rivet. If the plastic ring is broken you will need to drill out the rivet and replace the ring. Scamp
also sells a package containing the correct ring & rivets sizes as well. The caps are cosmetic only.
You can also get a new foam gasket for around the door from them as well.
I use 3M super 77 spray adhesive to secure loose rat fur but some people like to just use hot gun glue for more accuracy when doing only seams.
I have used a Woolite carpet cleaner to clean the rat fut on the bottom of my door. Vacuum the door well first and dont over scrub it as the rat fur tends to grow long if you do. ;-)
I have a 92 Scamp that spent the first 16 years of its life in the Idaho sun and had a pretty caulkie fiberglass finished. I used 3M Marine Restore and Wax with a wool power buffer to get it to shine again. If you google the site you will find that there are many ways of cleaning up the exterior.
Have fun with your trailer.