2009 has NTG4. If you have COMAND (satnav) you can buy an aftermarket integrated kit to go in - the in2digi D-MB-1 with a front windscreen antenna (very discrete) that fully integrates (i.e controlled as per your manual).
The D-MB-2 has just been released for newer cars (NTG4.5), but within a couple of weeks should have software to use it on the NTG4 cars, so talk to Comand Online and they can tell you what works
The advantage of D-MB-2 is it uses the same antenna feed voltage as Mercedes OEM tuner will do, so it can be made to drive the factory antennas so you don't even need a front windscreen antenna.
They are reasonably simple to fit, but it does involve a permanent power feed and fibre optics and a bit of configuration work.
Cheers
Richard