Welcome again Joseph!
It looks like the others have you on track with brochure and door rebuild info. New RV doors are not easy to find, and they are expensive. Many of the new ones are radius corner on top, not square corner. It definitely is a lot easier to rebuild the wood frame on it, if you are a little handy. Hopefully the plastic skin isn't cracked, but if it is, you can buy similar plastic at Home Depot in a 4x8 sheet.
When you're all done, seal up the bottom edge aluminum frame of the door when you reinstall it. A bead of silicone won't be the best, but it's better than nothing. Roof sealant would be best. If you can coat the edge as you push the trim on, that should ensure really good sealing. The reason the wood rotted to begin with is due to poor design- water seeps down between the texture bubbles of the plastic skin and is soaked up by the wood over the years. Filling the gap between the plastic and aluminum trim will help prevent water from getting down there.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR