First off do you have an owners manual, if not contact ONAN giving them the serial and model number to ge a book. With that many hours you may need burshes or is it has set idle yoou may need to use a piece of very fine emory cloth or a comutator cleaning bar to clean up things.
As to the type of set up you have you may need to contact Winny and have them send you the appropriate books for your unit
I ran my fuel tank too low and picked up trash and it blocked the filetr. Blowed it out and it ran fine. There is a small switch on gen that shuts the power off to 110 in motorhome. Found this the hard way also.........good luck