Product review (5 stars): Arrived quickly, installed easily, and it works.
The Whirlpool Refrigerator P.C. Control Board Kit arrived in good time and good shape.  It installed in the freezer compartment with no gotchas or unforeseen problems.  (Just be sure to unplug the refrigerator before starting the installation.)  The fridge has been making ice again for a month now, with no apparent problems.

One thing that I found online that was a big help was a technical service manual (Part No. 4322658A) for the Whirlpool and KitchenAid in-door ice system.  It helped me to understand how the ice maker works, how to diagnose problems with it, and how to perform installation of the optics boards (among many other things).