Roof damage repair

[GTS]

New PUP owner. Did not research well enough what to look for before purchasing my first popup, I suppose so got a surprise today. Went out to remove the old sealant to prep roof for paint. Thanks to an error I made I discovered the side panel was wet and totally rotten. Unfortunately the damage had gone so far that the 2 of the bolts holding the lift post at the rear had already pulled through and the top of the post was beginning to push into the ceiling. A little further and it would have popped through the roof. The front post bolts had just begun to sink into the side. Before purchase I had noticed that the supports for the AC were beginning to sag on one side and asked the owner who had only used the PUP one time. So he seemed to know less about it than I did. Removed the trim and now have to figure out how to remove the side panel to repair and replace the wood but not sure the best way to support the AC unit to prevent further damage. Also not sure what to use as replacement material as it seems the MDF or whatever had some kind of paper backing. Any suggestions and help would be appreciated. I am by myself and won't be able to remove the AC unit so have to do this from the ground outside. Thanks