What is the story on the Nav and radio? Does it come with cd or changer? What type of Nav is in it? Is the radio a good one? It does not appear to have a large color screen only a small one by the radio. Does it mainly work through voice? I wish BMW didn't put such a fancy looking site for the z8 but one with more info. My dealer doesn't know as much as I do. They apparently didnt even realize I got to choose the color until it was painted silver.