If you're wanting the steering wheel controls to work you have to have a clockspring out of a car that had them. I'm not sure how the 04+ are but the 97-03s have 3 connectors(IIRC) under the knee panel. There's metal frame work to the right side and the connectors have clips that just slide on. One of them is for the steering wheel controls on 97-03's. Could always check to see if yours is setup the same way. If it is then all you'd prob need is the clockspring since the harness is attached to it.
And yes 21MM regor.