Looks like we had a similar problem. Except someone backed into my driver-side panel in a parking lot. When I removed it, found similar water damage. In fact, the second time water damage - first time was passenger side.
I removed all the panel, insulation, and filon. Bought a 3/4 inch marine plywood, backed it, and now have a solid panel with no interior to rot. I found a near same color, sealed it and painted it with several coats of white exterior paint.
I'm on the road for the moment, but when I return (couple months) will post up photos. As I've read numerous times, Lance and other mfg have a tough time with these panels due to wood rot and water intrusion. SO, I eliminated the problem with solid panels. A new coat of paint each season and a caulking the seams again should keep it nice and fresh.