Why do you need an Arduino? Just connect module serial port to empeg serial port (need level shifter) and run code on empeg.

Admittedly Arduino would probably be easier programming wise to get going.

Be aware noise, ground loops etc might be an issue. Looks like it should do I2S which might be cool to get running keeping it digital all the way through to the car headunit.
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)