Not to confuse you further, but your Southwind did come from the factory with three batteries. It had one 12V starting/chassis battery and two 6V (series connected) aux/house batteries. Apparently, someone, somewhere, has replaced the two house batteries with a single 12V battery. Not unusual, but you probably will not find a photo of your current configuration. We still have some early '90s Fleetwood owners here who may be able to help.
It's unlikely that replacing a headlight had anything to do with losing the TV and Micro from shore power. It sounds more like a problem with your 120vac transfer switch/relay contacts stuck in the generator position. The transfer switch is mounted on the back side of your main circuit breaker panel. You might try giving the breaker panel a good rap (or two) with a rubber mallet or something similar. Sometimes this will jar the contacts loose again.