Thanks for the advice! After deliberating over the weekend (actually I was working double shifts all weekend), I set to work taking the ECU out of the transmission I took out of the truck. After removing the Valve Body I figured out how to get the ECU out.
Moving onto the new (used) transmission that I already put into the truck I was able to do the same. I then did the switch-putting the old ECU into the new (used) Valve Body.
I re-installed the assembly into the truck.
Serviced it up and what do you know, no faults, drives great (so-far).
Thanks for the help!