Onan generator replacement

I know they are few and far between these days, but try to find a small electric motor rewind shop and see if they can rewind it for you. Also the rotor and stator both have coils and hopefully both aren't bad. Have the shop test and determine which it is. Also a good motor man/winder may be able to repair the fault without a full rewind if the problem can be located without damaging the coil turns around it. The $5000.00 quote is ridiculous. Look at used onans where RVs are parted out and the will be thousands less for the entire unit.
Good Luck with this. You can do it much more reasonably than for 5gs.