operation of cell phone through audio system

If you have an Auxiliary jack in your stereo system, you should be able to do this. If you do not, you'll need an adapter kit. Are you just looking to use it as a speakerphone? Perhaps an Ipod adapter kit will work fine for this situation.

I had an 2000 E430 which had an auxiliary port on the left side of the glove box. If you don't have this auxiliary port then you will need some sort of kit.