I just bought a 2007 Q7 today!!

I have a question for the experts here, my Q has the ipod interface cable, but doesnt have the Audi Music Interface. I am a big dork and want to see my songs on the MMI, and was wondering a couple of things

1. What part would I need? Do you know the number, it seems there are some 2nd hand ones out there
2. Where to get it installed? Dealer?
3. How much would it run me to get it installed?

Appreciate any of your assistance.