Hey Doc,
I'm in the process of doing that. It appears that the wiring is there for the power, but not the heat. On my car the fuses are in the fuse box but the relay is not installed. Get relay # 5104857AA, ($26 @ your favorite DCX stealer), it plugs in behind the left hand lower dash ( you'll have to remove the lower dash panel)next to the steering column and you should be good to go.