Funny thing... I was just talking to Ron about this...
I think this has been talked about before but I could not find out where... anyway this gizmo is what you need:
you wire it in where your steering control wires meet you radio and program the "Pac Swi-X" to do what you want with each of your steering controls. The infrared does the rest to control your new head unit. Sounds great but have yet to find out for myself.
here is a link with some reviews:
link