Hi,
Sorry to hear about your bad engine. Hopefully it will be repaired and back on the road soon. I was thinking that they might take that engine out the bottom of the RV, so a large lift would be required, but not sure how it really is done.
I think that GM still sells the crate engines, I would be checking those prices instead of looking around the junkyards first. IF the crate motor is not that much, I would rather have it's warranty than to spend $2,000 in labor to install a questionable motor. You pretty much just need a stock GM crate engine rated for RV use, and they are fairly basic ones, though they also sell high performance engines in the $10,000 range with upgraded crank to rods and pistons rated for a supercharger. .
Good luck,
Fred.