I put the Harman Drive +Play in my car using the AUX input.
Anyone who says there is not an AUX input on the stock head unit is wrong. Unfortunately, to use it you have to have XM.
Anyone with XM that needs help let me know.
The Harman kit is expensive but very nice. AI will have a kit available in a few months to adapt to GM LAN. It should be about $100 or so.