First things first...do you have the 6disc CD changer in your glove box? If so go ahead and do the following, but if not then I don't know how to help you. You purchase the MOST iPod interface from the dealership and do the install YOURSELF. It is extremely easy, the OP posted spot on directions. When I did my install I didn't remove the glove box door as the OP did, I just left it on, my hands are small. Follow his pictures on the the first page but you're simply unscrewing, unplugging, replugging, zip tying. That's it.
The zip ties are the hardest part, a little tedious, also the ones that come with the interface are really stiff and one of mine broke while trying to tighten it, it's not a big deal but just be cautious of that. I found it easier to loosely clip the zip ties on first, THEN insert the interface and tighten down.
I went ahead and purchased the face plate, I like it, a couple people on this discussion talked about drilling holes into it and running the wire through but if you clip on the faceplate first, there is JUST enough room ABOVE it for the wire to fit, even when closed. So that's what I did, no drilling necessary.
It is controlled through the iDrive controller and on the screen, just plug in your iPod and leave it in the glove box. It will also work with an iPhone, the iTunes portion can be controlled through iDrive but if you want to play pandora or youtube etc. you have to disconnect the iPhone first, open up whatever audio app you're trying to use on the phone then plug it back in. Make sure the CD (iPod) choice is selected on the iDrive then wait about 15 seconds and it will override and play the audio. I think I covered everything but let me know if I can be of any more help