I recently got a cd-changer installed in my CLS with the help of Kevin M. (Thank you, thank you!)
I purchased the changer online, and found out that I needed to purchase an installation kit. Luckly, my local dealership had one in stock. Once I had all the parts, it took me 10 minutes to install the whole thing. No kidding. I don't even want to know how much the dealer would charge for this simple job.
Installation Kit includes all the parts you need. (B67 82 4024) - Fan, two fiber optic cables+plug, couple cable ties, bag of screws, and power cable. In my car, power cable was already pre-wired, and all I needed was the fan adapter, one optic cable+plug and two screws.
You are basically inserting another fiber-optic plug in the ring. CD changer will be attached to the "ring" using that new plug. One of the pictures below, I am holding on to two plugs. Left one is for the head unit, and the right side plug is the new plug for the changer.
From left to right, there are 1 through 4 cables. Cable 3 was originally in the hole 2. To add another plug 'A211 540 31 32' in the chain, I removed the original cable 2, and plugged that into the open hole(hole 3) in the new plug. Finally plugged the optic end of the new part(cable 2) into the hole 2 to close the chain.
Hope that somewhat makes sense. If you need details on the installation, let me know. I've taken many pictures at each step of the installation process.
Cheers!
Daniel.