Good luck on the iTrip. The reviews I have read haven't been very favorable. Lots of static and poor quality. In fact, I have a friend that purchased an iPod and iTrip. The iTrip was returned ASAP.
This is why I leaned toward the FM Modulator. I figured a hardwired configuration was better then the broadcasting type. I was wrong. The hardwired FM Modulator was crap as well.
The only acceptable way to hook up your iPod to an in-dash cd tuner is if your tuner has an auxillary input. Face it folks, all this other crap doesn't work. There's an old saying: Just cause you poor syrup on shit don't make it pancakes.
Take my advice, GET A NEW TUNER. Unles you like poor quality, static enhanced, muffled music.