Tough one to call Dave. Depends what locked up the engine. Lack of oil, or somethin' else? Onan's are expensive to rebuild period. A lot of folks moved to a repower like a B/S Vangard engine or Honda. Small Engine Warehouse is the place to purchase a repower. I think the B/S Vangard repower kit runs a little over 2K the last I looked... Find out what caused the Onan to lock up. The Onan in my 620 when I purchased it from the previous owner was knocking big time. Turned out one of the bolts that attach the starter motor adapter to the engine block backed out and the flywheel was hitting it!  Put locktite on the bolt, cranked it back in and we're good ta' go! No more knock! Stupid stuff happens. Check it out......

Steve@B&B