Hey fellas, I just wanted to jump in and say that Matt's advice came in handy, but I think I can add on to make it even easier.
First, get the lexan he recommended from Lowes or Home Depot. It's thin and flexible. This job takes two people, but you do not need to remove the rivets.
- Clear out the old glass.
- Have one person stand on the outside and the other person hold up the lexan to the hole.
- Use a sharpie to mark out your template from the inside of the RV while your partner holds it up.
- Measure out about 1/4"-3/8" all around your template.
- Use tin snips to cut the template out.
- Remove the gasket.
- Here the path splits. You can either try to fit the gasket around your window and re-insert, or remove it entirely and use either silicone caulk or form a gasket to replace it and hold the lexan in place. I cut part of the gasket out because it was damaged, and reinstalled with 3/4 of the gasket.
You and your friend should at this point be able to fit the lexan window into the frame with a bit of elbow grease. Yeah, it takes a bit to finagle it into place. A putty knife helped a lot. I strongly recommend you use one.
- Once in place, remove the film that was protecting the lexan. It takes patience, but leaving it on while you insert the Lexan ensures it doesn't get scratched.
- Caulk your lexan into place with a very thin bead of caulk. Patience and practice is key.
- Let it dry and enjoy the day.
Should only take a few hours if you follow this process. Images linked.
https://imgur.com/WpVMIZq
https://imgur.com/XOwJICN
https://imgur.com/o1lAPjF
https://imgur.com/w5vvaWw