Can a leak be fixed, absolutely. It requires replacing ALL the rotted/wet wood with new wood. It requires replacing any wiring, cabinetry, insulation, etc that got wet or damaged. It requires taking off the siding and interior walls. It requires taking off the underbelly covering and flooring.
It can be done, but its expensive if done by a dealer. Unless the dealer got it CHEAP, its unlikely they would do a thorough job and still be able to sell it for a reasonable price.
For me, I would have to buy it at a cheap enough price that I could still afford to fix any potential damage.
While they can be fixed, I'd be leery about someone else's work... especially a dealer who will try to save as much money on repairs as possible. If I did everything myself, or had photographic evidence that repairs were made correctly then I would be much more optimistic about purchasing.
Good luck!
