I installed my aux cable in a more easily accesible location, in the ash tray. It is very slick looking and easy to get to. It is also hidden in plain sight.
I put a gallery of the images with complete walk through here
Walkthrough
It utilizes the cigarette asher and is right next to your cigarette lighter, so power and sound can run to your phone in the same line without having wires strung all across the car.
Finished install
I used this aux adapter I got on eBay that also came with the 3.5mm cord.
http://m.ebay.com/itm/BMW-E46-E39-E5...-/181823400452
Not bad for $18 shipped.