I'm the type that I would rather do many things myself than take it back to the dealer as I'll generally do a better job and know exactly what was done. So that said, I think if this were my RV, I'd invest in a couple wire wheels and get my drill and go brush off the rust underneath and then put a coat of rustoleum on everything I could.
The pics look like it's just surface rust but like you I'm sure, I wouldn't be happy about it. I'd just be scared they would screw one thing up for everything they fixed. But that's just me.