What PCB do you mean the one from the TCM under the floor on the passenger side? If yes there are only two possibilities why it have corrosion:
1. The drains for the rainwater under the hood are clocked and water comes into the crossfire.
2. The seal at the plug of the transmission is leaking and the oil goes over the harness in the TCM and destroyed it.
So you have first to solve the issue what gets the TCM to be corroded.
You can buy a used TCM (look at the Part number and software version to buy the same). I don't think a repair is the best option.