I have recently purchased a 97 Deville Concours. The original factory window sticker states that the car is already prewired for the OnStar system. The problem is that the original owner never spent the $900 at the time to have the head OnStar computer installed. I WANT ONSTAR. You cannot buy the parts new obviously. Does anyone know where I could find the necessary unit used? Or how hard it will be to integrate?

PLEASE HELP!