Not sure about your S-class, but for most it is worth bearing in mind that the you control the iPod using the steering wheel controls and the track info, etc only appear on the instrument panel and not the Comand display ....
Unless it is a dealer (or specialist) fit accessory, the aux (ipod) connection is a 2.5mm jack connection in the glovebox. If you use this is does not give you the ability to control the ipod/MP3 player via the MFSW controls.