I have a 2005 Audi A6 I purchased used and it did not come with factory Nav or sat radio. I already have been told that I can install the XM radio by just plug and play, However I do not want sat Radio I want to install nav. I can find a used unit on ebay for $300 used and it comes with a older Cd. I need to know how exactly to install this unit. Do I need cables or any harnesses because many people tell me different or is it plug and play? Do I need to update my audi MMI because it has not been updated for years ? BTW in the back I have 2 Fakra cables one Green and one Brown and a Optical Loop Cable. PLEASE HELP ME I HAVE BEEN RESEARCHING FOR MONTHS!!! Thank everyone for your help in advance