Start by disconnecting battery negative.
Remove old PCM and install new PCM.
Reconnect battery.
If you have an old or weak battery connect a charger, this is a 45 minute process. If you screw up you are going to have to do it again.
On 05' up at least setting the emergency brake does not disable the lights so just turn them off if you need to.
Turn the key to the start position and release it to the run position, car will not start and DIC will say "Starting disabled due to theft system" leave key in the run position for 10 minutes.
Turn key off for 10 seconds, then to start and release. Wait 10 minutes.
Turn key off for 10 seconds, then to start and release. Wait 10 minutes.
After the Third time turn the key off and then start the car, if done correctly the car will start, the DIC may say Security relearn NOT done or finished when you turn the ignition on, but go to the start position and it will start.
I let the engine run for several minutes as it finds it legs and settles into a proper idle.
Now go drive,
Jeff