Ha! Like I always said.. When it comes to this info or anything to do with coding and combox, unless you're willing to pay, you won't get any help.
I believe it won't work what you're trying to do. His will work in your car but you'll need to rewire it... Since he's selling his, might be better letting it be. I'm looking for combox as well and believe I'd be able to code it myself... Maybe ;-)
2009 e92 ///M3 Jerez Black
2009 Audi //S5 Phantom Black
2002 e46 ///M3 Carbon Black
2007 Audi //RS4 Dolphin Gray