Hey scrapiron - thanks so much for the quick reply! I opened the door back up last night, followed the wiring diagram to see where power should be coming into the main control board - no power. OF COURSE I SHOULD HAVE CHECKED THIS BEFORE REPLACING THE MAIN AND DISPLAY BOARDS - ARRRGGGHHH!!! So I followed those wires back down to the bottom of the door and BINGO!!! You were spot on - there were actually three
broken wires. I had originally assumed this was unlikely because there is a nice plastic cover to prevent this where the wires run under the door. How three got broken at once, who knows - I am betting one of the kids pushed down real hard on the door by accident and just forgot to let their old man know.
Of course the wires are broken in such a position that I had to partially disassemble the entire bottom of the dishwasher, but I will get it all back together tonight.
Moral of Story for other Dishwasher Rookies: Start with the wiring diagram and a voltage meter first, replace parts second (of course this assumes you are handy enough not to shock yourself - otherwise call a repair person). Cost wrong way = $175. Cost right way = $1. However, I will say that I learned a hell of a lot more about dishwasher repair doing it the wrong way.