It is the dealers responsibility to maintain the seals on the camper until it is sold, then the responsibility shifts to the owner. It is obvious that the dealer didn't do this so he should fix at n/c. The manufacture can't be held accountable when the camper was on the dealers lot, out in the weather and not maintained.
I owned this brand of camper in the past, always did the required maintenance and never had 1 problem. I know who bought my camper, when I traded it, and they are also enjoying a problem free product.This manufacturer builds great campers and stands behind their product.
The OP bought this unit at a substantial discount or he would have bought new. Pick your poison.