Generator prep can mean a lot of things- the last rig I installed a 5.5LP in was "prepped", which included a sheet metal enclosure put right where the motor for the landing gear was totally inaccessible. I would up moving that, adding extra bracing underneath (I don't like to support a genset with sheet metal, even though that's what the "prep" package had, so I added 1 1/2" angle iron), cut the holes in the floor, run the new LP lines, run enough exhaust to get it far enough away from openings that *I* felt comfortable, then line the outside of the sheet metal enclosure with 1/2" plywood and carpet, then rewire the main breaker panel because the geniuses has put both air conditioners on one leg.
It's not just a matter of plopping it in and hooking it up.