I see some of my comments have made it here before me... :wave
Photos of most of the below are in the following thread:
New cabinate doors:
I used 1/2" furniture-grade plywood for mine. Had it laying around so it was cheap.
Sealer for belly band:
I think nothing special is needed on most eggs. The halves are glassed together. The Aluminum belly band is just trim to cover the seam. HOWEVER - in the spirit of utter paranoia I cleaned out all the old caulk and filled it with new paintable caulk (same stuff as below).
Replacing seam tape:
As noted - I pulled what little was left, filled the gaps with paintable caulk and then painted over the whole mess. Not as seamless as the photos would imply - but still quite nice.
Trim for roof vent:
The vent on my Boler is a small non-standard size. The inside trim is hand-cut from aluminum stock. I would imagine something similar could be done in your situation. Course - if it's a standard 14x14 vent inside trims can be picked up from various trailer parts places. It'll still likely have to be modified though since the roofs of our eggs are much thinner than they are expecting.
Rivets and bolts:
I used this basic proceedure for anything (rivet or bolt) that went through the outside of my egg. Made it through one summer's worth of storms afterwards - but no longterm data yet.
Paintable caulk was smeared around the shaft of the bolt/rivet so it would fill the entire hole (not just cover it) once the bolt/rivet was in place. Afterwards - I covered the top (or filled the inside of the rivet) with more caulk and smoothed it on the outside.
My decision was easy. The trailer had already been painted and the stripping wasn't gonna pull off everything, plus the glass needed enough repairs that restoring the original finish was out of the question. Well - that and the original finish was white over Avacado green (can you say '1972'???). I was glad to be rid of that.