I changed out the head unit in my S60 with an aftermarket Alpine. Not a real big deal. The only problem is you don't want to unplug the CCM. That will throw the SRS system out of whack. I think if you have to unplug it, you have to make sure the battery is un-hooked. I have not done the download to disable the AUM, but I have no problems and no messages showing up. However, I have to have the car in Monday and I will have it checked for stored codes.