I spent about 4 hours Saturday morning installing a MoBridge A2010 IPOD system in a 2008 E350. The car came with the IPOD cable option but the fact that it was not controllable via the COMAND unit made it very cumbersome to use... hence the aftermarket installation. I've used cartronics.com for a 2005 SL500 (IPOD, Bluetooth, and Video in Motion systems) and have always received timely responses to any questions. Their videos on the installations are great references. http://www.cartronics.com/Supportvideos.html
Another good source is petersautoradio.com
I've outlined the basic instructions below from my notes but may have missed a detail or two. Hopefully this will help those that want to go this route.

Put parking brake on
Insert key in ignition
Move shifter to neutral
Open ashtray
Pop up / out ashtray tab
Take out bottom ashtray
Lift up on gear shift plate pulling from underneath the front (required a bit of effort)
Disconnect indicator light connector on underside
Lift shift plate up, rotate black ring on bottom of knob
Pull up on knob firmly, supporting plate until knob is free
Put metal shifter back in park & take out key

Remove 2 torx screws under glovebox
Lower foam / plastic shelf
Route 2 wires from MoBridge unit from glovebox to center console (I had to get a firmer wire to use as a pull string of sorts)

Looking under the CD player in the center console:
Push tab of fiber connector to side to pull out
Push back blue fiber retention plug on connector
Remove side with arrow marked out (away from device)
Attach fiber (just removed) from harness to MoBridge connector
Close connection
Take other fiber connection and put that in the factory harness
Close the blue plug
Reinsert factory connector
Tuck wires in console

Pull out connector (brown & red wires) from under cd player on right side
Connect 12 V supply of MoBridge to Red wire of CD changer
Brown wire to brown - ground
Red wire to orange - power
Don't connect to the cigarette lighter as that's not a constant and each time you turn your car off, the settings and song selection will be "forgotten"!
Plug in blue power connector to MoBridge unit
Press white dot on side of diagnostic bipass switch
Plug in ipod, turn on car and press Audio and select AUX or CDC to test

Pull fiber wires back in to glove box shelf area (will make more room to reinstall the ashtray
Tiestrap / tape wires, IPOD unit
Place shelf back up under glovebox with 2 torx screws
Place ashtrays back in
Put key in ignition, put car in neutral
Put shift plate over the shifter, push knob down, turn black ring
Connect shift indicator connector
Press shift plate down into place

Notes:
My installation was a bit funky in that I had the Mercedes IPOD cable / Black box unit under the glovebox. When I removed, the car would not sense when the engine was off / key was out of the ignition and would continue to run. I've left the box in for now, but will continue to investigate a) removing the comand unit and seeing if I have to unplug anything from there (or the CD changer) or b) whether the dealer has to "unprogram" the AUX functionality via software
If you don't have the IPOD option from MB, your install should be simpler
Also, I needed to use the loopback adapter as plugging in to the CD connector did not work.
All in all, it took the better part of a morning to do the install... nothing difficult, but as I mentioned, had to do some troubleshooting on the loopback and "the box" to make sure everything turned off.

The MoBridge system is pretty easy to use, in that it converts your 6 cd changer disks to represent different IPOD filters (i.e. Artist = Track 2, Album = Track 3, etc.) Track 6 (options) enables you to configure different settings for how you select different Groups, Albums or tracks - and you can also control via the steering wheel.

 

Can you still use the CD changer with this?

 

Generally so as the system will use the CD changer disks as menu options (2 - 6). See a few technical notes below.
Technical Notes:

• If you have an External CD-Changer (usually found in trunk, glove box or center console) it must be disconnected.
  • Internal CD Player/Changer is not affected or disabled. Internal means inside the radio.
  • Some Mercedes have a CD Changer below the radio "In-Dash". If its separate from the radio and physically connects to the radio, then it must be disconnected. If it is a part of the radio, then it wont be affected.
    • General Rule - if you have a Single CD Player and CD Changer, the Changer will be lost.