You can restore factory configuration by installing used 10 disk Becker, or you can go with aftermarket Alpine 6 disk unit and adaptor. If you car still has original radio I'd suggest you look in the trunk behind left side liner and see if you still have original cable for the changer. This cable you will need in both cases and its about $100. You need to look for the cable hurness with two DIN connectors and black power rect. connector with red and brown wires.
If you go with Alpine you need:
Q-6-82-0135 -- software interface $135;
Q-6-82-0174 -- adapter harness $50;
Q-6-82-0175 -- cable set $98; (Only if you don't have it)
Alpine CHMS630 CD Changer $184;
Peripheral adapter MBZALP9 $37
These are the prices I paid when I did mine. If you do need a cable Q-6-82-0175, I have it for sale as well as factory Becker changer and bracket from my 92 600SEL.
Reg. Mike