I have a 2008 Quattro cabriolet with factory MMI Nav head end And phone prep in console. Bluetooth not working. Battery drains after a week or more of sitting. Dealer says bad telephone Bluetooth module and wants $1600 to replace. What is correct part number? I think it is 8PO-862-335-R, but unsure. Is the module located under the passenger seat? if I buy used, tested,,returnable unit, will it have to be programmed by a dealer? Also, if I replace the head radio/nav unit with aftermarket Pioneer or Alpine, will i still need a working module?