Thanks for all your advice, guys!
We have been working with the dealership (it sort of feels like that's the only option right now, from my research I don't believe we have any actual legal grounds to get our money back - lemon law etc does not apply to used coaches). They took it in yesterday for repairs and claimed that they would put in a new skylight, reseal the entire roof, ozone the unit to kill mold, and take out the carpet (we want to put in vinyl wood floors anyway, and it will allow us to see how good of a job they did).
It's been sort of exhausting and we can't afford a lawyer. They're doing all these repairs for free, as they should. My thinking is, they do this all the time and if people had legal grounds to sue them, they would be out of business. So you're right, I am learning a hard lesson, and the money I was previously "throwing away" on rent seems a lot more worth it now ;)