I replaced the thermister. The new part has a short wire and ends in a sensor; the original was longer and ended in a screw-eye that was screwed to the wall like a groundwire. But the business end matched, so I plugged it in. No splicing, far end is dangling.
When I turned the power back on, lights that had been off in the fresh side came on suddenly, then I heard mild clicking in the big black box (where the real business is conducted) above the freezer/cold compartments, and the lights went out. But the touch control in the fresh side seems to be responding, so the thermister did something. All fresh side lights have stayed out and 2 bottom drawers (each with their own temp settings, lights and touch panels) are dark. Also ice/water dispenser (also has its own lights and touch panel) is still dark.