hello i have looked about for ages and not found what i need can any one pls help, i have a 2006 a4 cab with Symphony ll fitted (one with ugly casstte) my friend as 2008 a4 cab both have non bose and no phone or any thing else just basic unit but his as Symphony ll+ (mp3) can i stright swap or what do i need to get this in and working any links to wireing loooms and guides would be greatfull only thing i can find is about areial but i dont under stand it what so ever many thanks