First off I'm looking to install my new Dension Icelink and I need a radio key to take out the head unit yadda yadda yadda. How many would I need? There is tons on ebay for a couple bucks but would I need 2 sets or 4 keys to take out my Symphony head unit? Its in an 03 a4 with the indash cd changer. Also will hooking this into my deck affect my cd changer? Cuz on the box it says to plug into cd changer spot. Thats only if i have an external cd changer right? Anybody else installed one of these? Anybody in the Trenton or central Jersey area?