I was able to do service on my 6500 on 35' LY last fall without removing it. This included oil, filters (propane, oil and air), plugs and something else I can't remember. I don't think I would try to remove mineand would probably take to a service center. If you have a Cummins dealer or center near you they also own Onan. looking at mine, I think the exhaust could be done without removing the set, but again I would probably defer to Onan. They do have a tech support line and are very helpful. Go here to start:Cummins Onan RV Generator Customer Support
At the bottom of the page click on the contact us link. Luck!