After thinking to myself, how could anyone reverse polarity when hooking up battery cables, and saying "black is positive, white is negative", the senior moment hit. I did exactly what I knew could never happen - I hooked the cables up backwards.
Fortunately it got the reverse polarity fuses, which I replaced. I didn't find anything else, but we were getting ready to leave so I didn't check everything. At the campsite, the radio wasn't working, and I figured there was a fuse behind it. There was. I removed the radio, replaced the fuse and success. Fridge worked during campout, but we didn't use the water heater or furnace, so I guess I still need to double check on those.
Anything else you folks think I should check?
Mike