1982 380SL Becker stereo wiring
 

HELP! I have a problem...my car has had an amp and speakers installed in the rear deck a LONG time ago. The speakers were dated 1985 and the amp had an old school DIN input (I think that's what it's called). The shop put in a speaker level to RCA output adapter and the amp was wired poorly. The turn on lead to the amp was wired into a green and red striped wire with a spade connector to the black wire in the plastic harness. My main concern is that the brown (ground?) wire in the plastic 4 wire harness is a ring connector that was attatched to the Becker stereo with a bolt on the back. There is also another brown wire with a ring connector that splits into two brown wires. Are you suitably confused? Can I run a new ground wire to a bare metal spot like you do with a car amplifier or what? I can send a picture via email if that will help...
Thanks,