Update:
It's the 120V fuse which kept blowing. And it wasn't a tech at Norcold which helped me do the reset; it was a mobile RV tech, who services Norcold, who stepped me through it while inching along a typically-jammed southern California freeway.
Well, we've started to smell ammonia, which I understand is a slam-dunk indication of a bad cooling unit. Lovely. So, now, how should I proceed? My shop is suggesting I order a brand-new OEM unit for about $1,200, plus 3 hours labor to install. Just wanted to run this by the forum for opinions and options.
Dave