Its in the passenger side rear panel, ahead of the sub (if it exits) or junk compartment in the pannel. Don't try to rip out the junk bin, all the plastic tabs will be ripped off and it wont go back in.
You have to remove the panel, if its a 2 door you will have more fun (remove back seats and both seatbelts), if its a 4-door shouldn't be too bad. You're gonna need a t-50 (and a good quality one at that) to take out the seatbelt bolts. Pull back the floor carpet and there are 4 or so Phillips screws holding panel to floor, then 2 more moving up the back by the hatch, a bunch of christmas tree fasteners around the window, and the coat hook (and maybe a screw or 2 more, I forget, just look) You can get away with just removing the seatbelt pivot (the part at the top), but the panel will still be stuck to the wall by the belt. If you want to remove it all the way, make sure you go underneath and clean off and lubricate the seatbelt bolt that goes into the floor before you try to unscrew it.
Then you can splice wires into the factory speaker wiring and hook up the radio that way. There is enough space under the door sill to run the wires to the front. Don't use one of those stupid adapters that lets you hook the radio to the amp connector, it sounds like crap because the amp is a peice of garbage. I can get you a wiring diagram if you need it....
