Actually there is a better way. Get one of these.
It's made by Peripheral and provides 2 RCA auxillary inputs. It connects directly to the back of the REC unit; no cutting or soldering. It's plug and play. Works great. I used one on my '05 without issue. Just 2 requirements.
1. Plugs in and emulates SAT or VES input in rear of radio. Thus must sacrifice one.
2. Must still use ipod directly to select music. A nice mount can keep this still in easy access while driving. I used a Proclip mount. You can use the steering wheel controls to control volume and input selection. Remember I mentioned it provides 2 thus 1 can be for Ipod and other anything else.