Instrument panel light problems

[Darkcloud617]

To begin with, I have a 1998 jimmy, no real electrical problems at all, the people that owned it before I did took it off roading a few times and broke a couple of minor things in the car... like the glove box hinge and such. On any note, I just bought a new pioneer car stereo and plugged it in. To cover everything I done... took the dash off and pulled the stock radio out, then put a mounting kit inside of it, I had also bought a wiring harness from Walmart, so that was all correct also. I had unplugged the battery ground because I had to unplug all the toggles for the lights, 4x4, and such. After I put it all back together, the CD player was fine, came right on without a problem, also all the speakers worked fine. Happy me, new radio... until I turned it off, with they key all the way out and the door opened and closed, the instrument panel won't turn off (gas, MPH, gearshift light, a/c, lights,etc) the stereo goes off when its supposed to and the dome lights, also when I push the brakes, the brake lights turn on.... I dont even know where to begin with troubleshooting it, I don't have alot of experience with car electrical equipment, can someone please help me? I have to unplug the battery to get it to go off now.