The PCM is THE controller for the engine and transmission ... so it is all important to emissions control and engine performance.
But there is a far greater chance that there is a broken or grounded wire somewhere in the maze of harnesses involved ... than there is a problem with the PCM. I have repaired many wires on my Windstar, but still running on original PCM after 260k miles. The data link connector is a 16 pin device with 7 active conductors attached. It is connected to the PCM on 3 PCM terminals. I would suggest you buy a Ford wiring diagram for your model and to a pin-to-pin check on the related harnesses. Better than throwing money at who knows what.