So we decided to take out all the windows and reseal them. Taking them out was the easy part. Getting the 20 year old gunk off was the tough part.
We used flat head screw drivers, floor scrapers and wire brushes to get everything out. After that we resealed them with silicone and installed them back in the bus.
We used 2 inch insulation for the walls and ceiling. Luckily we found a guy on craigslist selling the stuff for cheap so that saved a couple extra bucks.
To make the curves we just cut lines in semi equal parts across and bent it to fit.