It's fairly easy to find, just remove the trunk trim on the left (drivers side) of the trunk, it's nylon wire-tied to the fender bracing, or may just be laying down towards the bottom of the bootleg.

I'm not into all this stereo stuff, but one advantage to the MB changer is that the radio will operate the changer in the normal way. Maybe there are other changers which the factory radio will also integrate with.

Gilly