How many hours on the Onan? Has it ever been rebuilt or torn down for any reason in the past? When my Onan lost half of it's compression, I dropped it off at my local machine shop. They tore it down and checked all tolerances. I'm going to need new rings and exhaust valves. When all the work is done I expect it will be less than half the cost of a Chinese re-power.
Just checked SEW and they do not offer a kit for the 982. A used engine would be a big unknown. Parts for Onans are not hard to find or all that expensive. Robert Kummer is a great source for parts and knowledge. Here is his contact info.
http://boomersonanparts.com/