Stereo and dash lights

I changed the stereo in my girlfriends 1996 ford contour. I baught the right harness and hooked it up totally right....only the left two speakers came on and they sounded horrible. I hacked the end off of the smaller of the two plugs ( the speaker to amp i think) Their was 8 wires and an uncovered ground. I touched all of the wires untill i figured out the l/r f/b and they all worked but sound like shit, they pop when i adjust the low pass frequency on the aftermarket deck. The problem i really have is that now all of the dash lights and console lights dont work, i didnt hook up the illumination wire to the aftermaket deck, i doubt that would matter though. PLEASE HELP.

The fuse for the dash lights and console controls the tail lights, too. Check them to see if they come on. If not, it's the fuse that's blown. As far as the unit you put in for your girlfriend, if the ground wire is hooked up, but the chassis (stereo case) isn't grounded to the car it will sound bad like that.