For question 1, here in the US a 2001 would have a cd navigation module and a 2005 would have a DVD navigation module. Make sure you are purchasing the correct media for your system.
For question 2, this is most likely a radio problem or an amplifier problem. do you have DSP? (digital sound processor) this problem is more common with the DSP option. The cheapest way to sort this out is to find a friend with the same system and swap parts, 1st the radio then the amp to try and narrow down the problem. if you dont have someone willing to do this for you then probably your only option is taking it to the dealer for diagnosis.