No, you are not stuck. Crank up your generator and let your inverter/charger do the work of the alternator by holding your boost switch down. Wedge something under it and you only need it on for 10 minutes/hour. Or buy a 10-15 amp battery charger and using your block heater outlet to power the charger (unhook the heater) and use it (and the generator) to keep the battery up while traveling home if necessary.
It could be the regulator or even a loose wire on the alternator. I'll assume you have a rear radiator so in your rear closet there should be an access hatch in the floor. OR it may be on the bottom of the engine and he'll have to slide under. Good luck and a $50 battery charger may be your best bet.
Where are you as I carry a spare alternator but I doubt on that new a MH it needs replacing.