Ice Dispenser auger won't stop dumping ice into chute
Short Answer:  Replaced both boards, and this fixed it.

Despite lots of excellent help from others on this forum, concluded that I couldn't adequately test the boards without risking damage to a new board by connecting it to one of my current (status unknown) boards.  Very appreciative of the caution regarding these parts' sensitivity to static discharge, as even the chat help person from the parts website didn't know about this (but the parts packaging confirmed that you need to wear a wrist strap grounding device and handle carefully to avoid damaging the new parts).