Your problem is that you have a 5 year old generator that only has 80 hours on it. That's not even one full day a year. Gensets need to be run - a lot and under load. At this point it should have a few hundred hours. It's better to run a generator 24/7 than let them sit not running at all. Hard to tell what's wrong with it since it doesn't get used. But your Onan was built for your RV. It's sized properly and fits in the bin, all the wiring is set up as well as fuel lines etc. I would get it fixed rather than buy another generator. Otherwise you have a lot more work to do, like where to put the new one, wiring it up, fuel supply, ventilation and exhaust, etc etc. The root problem is lack of use and maintenance. I don't see how buying another generator will fix that problem. Do you even need a generator? Seems like you don't use the one you have. Not trying to be snarky. But fixing this one will likely be cheaper and easier than buying another one and getting that to work in your rv.
On edit:
I reviewed a few of your other posts an it seems like you have an RV that only gets used 1 or 2 times a year. As a result you are having issues due to lack of use. RV's - like anything else - like to be used or they start to have problems. Have you considered that you may actually be spending more money addressing things from lack of use than selling it and renting an RV for the 1 or 2 times a year? Again, not trying to be snarky, just a thought.