"A bird in the hand is worth 2 in the bush!" But in this case, you have 2 birds in hand. It's a hard decision which way to go! You have 2 violable options.
I would think the deciding factor would be, has that water intrusion stopped. Is the leak stopped? If it's still leaking, and those walls are still wet, I think you'd be best to take the offer and sell it and be done with it. To fix properly, could end up costing you much more than $2500, and you could still have a gigantic mess on your hands.
However, if the leak is stopped and it's now dry, if can can clean that mold up without depleting your funds, you'd be better to keep it.
The rest of the camper doesn't look all that bad. If if doesn't leak, if you are not in a severe cold winter climate, a little caulk, a little attention and you can probably fix it up without having to invest a lot. Then in 2 years when you are finished with school, sell it.
Another question that needs to be answered, how much will it cost you to live somewhere else? As long as you can keep the camper parked where it is, rent free, I think you'll be better off.
Only you can decide though.
