BMW 730i CD system - CD changer

Guten tag. I will dieser frager im english sagen: I am the happy danish owner of a 1995 E38 730 IA. My car has the standard radio and cassette tape stereo integrated, but no CD. (see  http://www.reaktion.com/bmw/interior.jpg ) I would like to integrate a CD system in the car, either a CDplayer or a CDchanger in the back. My questions are:

1)How can I find such a CDsystem, and how much does it cost?
2)Does it have a special name or can I install anything? What about MP3?
3)Can I install it myself or will I have to use an official BMW dealership to install the CDplayer?

Any help would be appreciated, thanks for your feedback.

I can be reached at the adress wilmi@hotpop.com

Wilmi, Denmark