You will need a 10mm socket and a 7mm socket.
1. You will need to go undo the 10mm bolt that holds the harness to the PCM into the engine bay. Its located directly under the master cylinder. Using a 1/4" drive socket is the best. It takes a bit of time...but its doable.
2. Once you have that bolt undone...there are 2 7mm bolts that hold the PCM holder inside the truck...by the emergency brake pedal. Loosen up those bolts. Once removed...you should be able to carefully pry up and out the pcm. It will then come out of the plastic case. You should then be able to see a PCM code on the part that plugs into the harness in the engine bay.
Hope this helps.