You might tell the shop that plastic RV roofing material, Filon, is available on Amazon for $1,000 per roll for a 30 foot long roll, 8.5' wide.
I've read several DIY accounts of changing the roof and that might require some structural repairs but it's not that difficult of a job. I'd say 2 guys working on it for 6 hours per day could have it done in 3-4 days. What I don't recall is how they bent the flat Filon so it rolled over the edges...I can't remember. Maybe with heat guns?
Anyway, just giving this info so when you talk to a shop, they won't be trying to snow you. Or let the insurance company pick who does the job as they often have the knowledge to know who's good and who isn't. But if you get a bad vibe from the shop (I'd always go and talk to the shop before such a big job), check with RVServiceReviews
and other review sites.
Good luck, sorry about your roof.