Hapa88

My GF just bought a 2001 SLK and for some reason, MB can't find the correct unlock code to get it to work (they've had 3 different codes and they all don't work). So rather than bother with it, she'd rather have MP3 ability anyway. So I'm looking to get the Sony CDX-F7715X for her:


So I have a few questions.
1) I've read that I need a VW harness (what year??), but I was just at GoodGuys looking at the harnesses and the 1987-2001 VW harness has 2 plugs (2 retangular shaped plugs). Whereas the stock MB radio has 1 retangular plug and 1 square (3 wires in the retangular plug and 8 wires in the square plug). What harness do I need?
Her stock radio looks like this:


2) There's 1 extra plug in the back of her stereo that had two orange wires (one labeled Tel Out, and one labeled CDA in or something like that). What do I do with those if I install an aftermarket HU? Are they important?

Hapa88

This VW Harness that GoodGuys and everyone else sells. Looks like the top plug of the MB wiring will fit, but the harness won't work with the square one from what I can tell.

VW Harness by Metra #70-1784 (for VW cars 1987 & up)


VW Harness by Metra #70-9003 (for VW cars 2002)


This actually most closely resembles what might fit:
VW Harness by Metra #70-9002 (87 & up AMPLIFICATION INTEGRATION PLUG)