Hi. Hope some one here can help me. I am helping out a friend that just have purchased a TT mk1 1999mod. The car is equipped with a concert tape deck head unit. The unit is faulty by haveing a bad connection in the volume up/down nob. So now we need to change it. 1. Doese the concert "CD" swap directly in? 2. Can I use a unit from a A4 car! 3. Does it need any coding? 4. What is needed to get Aux-input Thanks for helping.