1990 chevy pickup factory stereo wiring

Is there anybody out there that can help me? I have a 1990 chevrolet c/k pickup that I had put a aftermarket stereo in my pickup and someone stole it shortly after. I originally had the step by step instructions on how to disconnect the factory stereo (It had the separate stereo and cassette player/ graphic equalizer). After I installed the aftermarket, I didn't think I'd need the instructions anymore so I threw them away. I need to know exactely how to reinstall the factory stereo. It has a little silver box that mounts below the dash that controls the stereo and cassette functions and separate plugs for everything that runs to or from it. Please help me out, any information will be greatly appreciated. Thanks again.Chilliphilli1968