You should be able to purchase access to MB services and then download wiring diagrams. In Europe that would be this site:
Daimler AG - Service & Parts net
This NTG2.5 appears on several current models but the units are physically all a bit different.
It would not have TV tuner standard but I don't even remember if there was an option for the TV tuner and how would that be wired. iPod would be the same as on your current Comand.
DIN connector (or ISO connector) is the standard radio connector that you can find on most after market European radios and also on all older (but not ancient) European cars. If I remember right, NTG2.5 would not have the exact DIN/ISO connector but mostly equivalent pins (but not all).
Is the seller at eBay? Can you give pointers, the €1200 price sounds like the seller got it for free (one or the other way).