Well, I received my parts for this today, so I went at it this afternoon.
Being as I had ordered both the complete PCBs and the transmitting and receiving optos themselves, I decided to come up with a specific approach. I started with replacing the transmitter opto on the existing PCB located at the mini playfield exit. After reinstalling, it still did not work. I then moved over to the corresponding receiver opto, replaced that on the PCB, and still no dice. I went back over to the transmitter side again, but this time installed the new complete PCB assembly, fired her up, and this time it worked.
Next, I moved to the top opto and repeated the procedure, starting once again with replacing the transmitting opto on the existing PCB. When this failed, this time I replaced the entire transmitting opto PCB, flipped on the power, and now that opto switch worked perfectly.
After this experience, I have determined that one of the following happened:
1) Both transmitting optos and their PCBs were fried when I mixed up the molex connectors, or
2) Both transmitting optos only were fried, and I damaged the PCBs when I was switching out the optos on those boards (a distinct possibility given my somewhat rudimentary soldering skills...but I am learning!).
Regardless, my TZ is now happy again. ForceFlow, I cannot thank you enough for your help and guidance through this. One of the many things I really like about Pinside is how everyone is willing to help everyone else when problems arise.
Once again, THANK YOU!!