Mercedes head unit problem

[bgp]

Hi all!

I have a problem with my COMAND NTG2 navigation system in my Mercedes GL420 (X164) from 2008.
The problem started about i know this car (2 years ago). Firstly i wasn't able to connect my phone via bluetooth to the radio (it's the smallest problem).
It said that it sarts the telephone but nothing happend, never.
About a year ago my rear view camera (backup camera) stopped working. Actually the camera system is working, I was able see it's pcture if I selected AV2 video input, when I selected reverse gear, but the head unit doesn't showed me the picture automatically.
And a few days ago it has a new feature: if i want to start it, it shows me the Mercedes logo and plays dead, nothing happens. I cant't communicate with it with my diag tools (earlier i was able to do it).
Does anybody meet with the same problem?
What is your opinion, it is a communication error between some modules or simply the head unit died?

If i want to replace this head unit, is it possibe easily or it needs some special tool?

Thanks in advice!