Indeed a very hard lesson and I feel for you.
First thing, STOP trusting that dealer. He probably got a better price for the original unit and sold it out from under you.
Never trust a dealer. Period. No matter how friendly and sincere, they are out for their bottom line and not for your best interest.
Expect what ever repair they do to be a patch at best. It will not be a total fix (which would cost many thousands of $) and you will likely having lingering issues with mold and rot.
If there's any way, get out of the sale altogether.
If you buy another unit, pay an independent inspector to check it out.
I wish you the very best of luck.
Scott