Replace the whole generator after three years? I can see yanking the carb and getting a new one, or perhaps a replacement genset if the windings are absolutely trashed, but I've seen 10+ year old Onans still in service, even with very spotty maintenance.
Only downside to how a generator is mounted in most Bs is trying to change the oil. I have a friend of mine who uses an oil evacuation pump to suck the oil out of the genset, then another pump to get the new oil from a bottle into the generator without too much of a mess. Another friend of mine just drops the generator with a forklift come oil change time, and does the job on the workbench.