When I was in the car business, until the customer took actual possession of the vehicle, then the contract wasn't fulfilled and they could still back out of the deal. Since you stated that you're not taking actual ownership until next week, you still should have some leverage. I would think that it would work this way in the RV business (but I'm not 100% sure)
#1. Call the bank to see if the deal has been funded yet. If they haven't you still hold all the power. If they have paid the dealership, explore what options you might have with getting the deal voided if the dealership isn't able/willing/interested in working out a deal that will be a "win-win" for both parties.
#2 Talk to the dealer. You can go in and be a "a-hole" right off the bat and probably get alot of resistance and reluctance to work with you, or you can work with them to try to find a way where you still get a camper that will work with your current TV and the dealership will still get to make a sale.
I really don't think it's "doom & gloom" at this point