All I did with mine was to clear out the ECU coding, recode the keys to the ECU (I think I only had to do this as I have immo3 clocks) fire up the car and job done
Install the new ECU in the car
[Select]
[17 - Instruments]
[Adaptation - 10]
Leave channel at "00"
[Read]
[Save]
[Done, Go Back]
[Close Controller, Go Back - 06]
[Exit]
Turn ignition OFF for 15 seconds. Start vehicle.
Or in my case, have the clocks beeping at you saying the immobiliser is active...