I am interested in modern connectivity to Audio 20 systems. I have a 2007 A150 Elegance with fairly high spec. There seems to be no external connection to the Audio 20 stereo system either in the glove box, central console or arm rest. I would like the system to play from USB flash drives as well as connecting via a standard 3.5mm stereo socket. If these show up some details of what is playing on the screen and can be controlled via the steering wheel buttons, great. If not, no big deal. I am reasonably handy with a soldering iron.
I would like to know a) what extra hardware I need, if any (what it costs and where to get it) and what its advantages are over not having it/making it myself b) what wiring I need to put in place c) how I set about the whole process (do I need to remove the radio unit to get at the rear connectors, do I just need to remove the glovebox etc.).
Any help much appreciated.