That's how we learn!
I purposely buy distressed campers, but I know the issues and know if I can fix them or not, so I have similar stories, just from a good perspective. Campers in general are so junky and poorly built that no matter how much you fix them they immediately start to fall apart again.. unless a skilled renno guy does the fix.
You did good to buy the fiberglass TC, those are golden, and whatever issues you have you should still have a solid shell. The sheet metal/wood exterior of most campers is their ultimate undoing.
And I bet you know why fiberglass foamcore construction models sell used for such high prices.
I have a fiberglass TC now and do not plan to sell it, but if I do will ask for a premium price, and probably get it. Mine is much better than when if rolled out of the factory, so the issues have been fixed and fixed well.
If you need advice on AC many here can help. I put a Cub 9,200 on mine so my 2200 watt gen would work, it cools the cabin very fast even on 95 degree days in direct sunlight. You did good there.
Your question #1 is, how to get it on the roof. Use an extension ladder if you have one. Park next to a hill, or lower the TC as low as possible, and slide the AC on a board using the ladder as a ramp, slide it as close to the hole as possible. Use moving blanket to protect the camper from the ladder, and be careful to not let AC fall off.
The rest of the install is easy. Wiring > green wire to green wire, white to white, black to black using wire nuts. Your cub will have indicator marks for how much to tighten down on the gasket, so its all easy after u get it on the roof.
