ok jay, this is REALLY easy, I did it on my 95 xlt not a month ago
First, go to crutchfield.com and order the amp bypass wiring harness from them. They can also give you a mastersheet that tells you everything about your car stereo stock system, with pictures and all. But basically, you are going to solder the wires that are on the harness to the cooresponding wires on your hu's harness. The colors will probably match, but just read the instructions for the harness and the deck to be sure. Now, the bypass harness is going to have two connectors , one that has about 12 feet of wire coming out of it goes to the amp in the back in the trunk. The other has a few short wires that hooks directly to the connector in the dash. What you need to do is take out a few screws in your trunk (this is where the mastersheet comes in nicely) to disengage the trim, then pop out a few trim pins, and you can see the amp (right hand side if you are looking at the trunk from the back). Pull the plug from it and plug in your harness. Route the thing from there back to your dash. Use a coat hanger to pull the whole harness up to the stereo. You will have used radio removal tools to pull out the stock radio by then of course. After that, you just stick the hu in there (complete with dash conversion kit to make it fit in the opening) and plug the connector that came with it that is now woldered to the bypass harness into the radio, and you are good to go. Make sure your battery neg is disconnected the whole time. Then go reconnect the battery and you are good to go.
Definately do not integrate the factory amp. Best of luck, it really is not as hard as it sounds. If you have any other questions, holler.