Sure....

The AUX cable plugs into the back of the radio. When you do this, it enables the "AUX" function of the radio when you push the mode button. You plug your iPod into the recepticle and press "mode" until you see AUX, and voila, you have iPod sound. The installation is pretty straightforward, but running the cable from the back of the radio to the console was a bit of a hassle. I had to use a coathanger to reach through, taped the cable to it, and pulled it through the console (under the cupholder) to the compartment under the armrest.

The sound quality is pretty good, I'd say a 7 out of 10. There is some backround feedback, a bit of a hiss, but you can only hear it if you are sitting in the car with the engine off. Right now I'm using the headphone jack for the output on the iPod, but i understand that there is an adaptor for the bottom that allows you to plug into that port on the iPod and gives better sound quality. Perhaps someone can confirm this?

I chose the very basic $40.00 AUX cable (geunine BMW part). for more money, you can get the "iPod integration cable" that will allow you to control your iPod through the stereo and steering wheel buttons, but for me it wasn't worth it. I sit the iPod right in the cupholder and it's convenient to just grab it when necessary. Hope this helps.......if you have more specific questions about the install, don't hesitate to ask! I utilized a combination of the instructions on the homepage as well as the ones that came with the wire...

EDIT: I would guess that the dealer would charge you around an hour of labor or so for the install.