A maintenance free generator (or any RV, or anything RV related) doesn't exist. While it is true you can keep buying generators to avoid doing maintenance on them, it's not very cost effective. Like I said before, not trying to be snarky, but if you don't have the time to take care of it, don't use your Rv except a few times a year, you could probably save a ton of money and aggravation not owning one and renting instead. As you are finding out, not maintaining your RV leads to problems. Those problems lead to more time and money you already said you don't have and an RV that is depreciated greater than it should be if you ever decide to sell. Good luck.
Back on track, I would find a cheaper place to work on your genset, fix it, and learn how to maintain it. I know you said you don't have the time, but look at the time and money you are going to spend now. It's much greater than the time it takes to do preventive maintenance.