hi, everyone im new here and i just bought a 99.5 a4 with the concert sound system in it. and i want to put in the nav. unit that audi makes but from looking at all the nav. units none of them will just plug and play. from what i found i have to rewire the hvac controls and ill have to move them. now my question is, is there a nav. unit just for this car or do i have to rewire everything?