to FiberglassRV, we're glad you're here
I'm willing to do a lot of things to my trailer myself. Replacing the wall covering is NOT one of them. Lots of work, lots of expense.
Ryan completed the ensolite replacement on his Trillium
Sportsman this past summer. It cost him (with glue) more than $1,500. He bought the ensolite from TrilliumRV which is very similar to the original.
Direct Link to Ryan's replacement post: Rebuild of a Trillium Sportsman
Based on this info, you may want to consider what Roy said. Do what you can to save it.