I've read so much info the past few days and still nothing helps me. My hope is this is not a special situation, so here it goes...

Im trying to connect my PHATBOX to my A3 (2007), look for "cd changer" plug behind glovebox and didn't find it. All info says it should be there but maybe that was just for 06. Dealer looks up VIN say's "not prewired for cd changer in your car". Ok here is what I need to know:

Is it a DIN or RECTANGLE plug?
Can I buy plug from ebay and go from PHATBOX directly to radio?
Or is CD CHANGER plug in rear quater panel?

any HELP will be much appreciated?