Without knowing all of the details it is tough to speculate what can be done. If the damage is minor to the cylinder walls, it can be honed out. They also make portable machines that can bore out one cylinder with the engine still in a TRUCK frame. I don't know if there is enough access to do that in an RV frame.
In either case, the rest of the engine probably needs to be dismantled to insure that any metal filings, etc have been cleaned out. This involves dropping the crankshaft, etc. This is usually followed with a replacement of all bearings once things are apart. The head may also need to be rebuilt once it is removed.
I had one diesel engine resleaved and it is still a major project even if the engine does not have to be removed. After watching the whole procedure and the tight working environment, I think it may have taken less labor time to drop the engine before doing the work.