I dunno if this works...
www.formymercedes.com
MP3 Adapter
#mp3-slk
The Bipes Automotive Portable MP3 Adapter allows you to connect your portable MP3 player or other portable audio device directly into your Mercedes Bose sound system.
* Plug and play – no cutting or splicing required.
* Clean, clear sound with no fading or interference as with FM modulators.
* Easy to use – no switches, tuning, or adjustments.
* No visible parts (except the MP3 audio cable). Stock appearance is retained.