It looks like you've got two places you need to focus. The side and the front panel. Both are FILON, a fiberglass sheeting material that's available at any RV service center or many online RV parts websites. FILON is relatively inexpensive, but shipping, because it usually has to be trucked to you, is cost prohibitive. As an example, a 20' length of 102" wide FILON at EBay is $525.
https://www.ebay.com/itm/RV-Fibergla....c100005.m1851
You can usually get it at any local RV parts/service center for much less because they have a delivery contract with their supplier and don't pay "freight charges".
If you do a forum search, you'll find several threads posted by members who have done similar repairs. Their problems, issues, successes, how they did it and in many cases costs are well documented with photos and pitfalls.
Any questions, let us know and we'll try to help you "figure it out"....
Good Luck