power to nav - so, you have the nav screen working.

is there power to the radio? is the little orange LED indicator next to left knob coming on? if the indicator is coming on, can you engage radio? or the CD changer, if you have one? when you tell navigation to direct you somewhere, can you hear navigation voice? If there is no little orange light next to the knob after you tried to turn the radio on/off, have you checked ALL fuses, both in the glove compartment and the rear hatch?