I just bought a vehicle that has this stereo in it. It worked fine, but I was pushing buttons in the dark and being unfamiliar with this stereo I pushed something now I have no sound. It's not the mute button...that's the first one I tried. I've tried pushing every combination of buttons that I could and nothing is working. The stereo comes on and I can hear the speakers 'click' when I turn it on or off or switch between tuner and disc. But no other sound...also, how do you hook up the mp3 to it? Thanks for any help...