Scottml350

Hello,

Need some help. I have a 2004 ML350, I have the single disk Navi, and optional bose stero. The Navi does not recognise the dvd and there is no sound coming from the speakers. First the navi stoped working, then the CD player stoped working. Now the radio does not work. What's weird is that cd player is stuck in the middle of a song, in radio mode I can flip through stations but there is no sound.
Some people tell me it's the amp, but somehow I feel it's the head unit.
I haven't opened the dash to check for loose wires, however I did check the fuses under the hood of the car and they are ok. Are there any other fuses to check, or could it be anything else.

Thanks,

Scott