I would take another look at the trailer. What you have there is a fantastic unit. Wish I had one of those. If you like camping and outdoors, then keep it and fix it up. Fact is, a new one is over $40K.
If you are not into outdoors and camping, and don't have a suitable tow vehicle ( look in the forums, there are plenty of treads on tow vehicles) then perhaps it would be best to sell the trailer.
Check the running gear first, if that's ok, then you can start using the trailer, even if soe of the interior stuff isn't working right.
This forum can answer very many questions, like John suggested already.
If your dealer wants $4500.00 to restore the trailer, then you will end up with a great trailer for just the repair investment. Most of us spend this much on a mostly functional trailer, and then as much over time to get it finished and personalized. But it much depends on the overall condition of the trailer. Hard to judge without seeing it.