are you going to install a new deck, or wire this to the factory deck.
i dont really know much about the wiring in a 2002. i had my deck put in professionally, since i dont like messing with wiring into the ignition, but you could probly get a wiring harness that would plug right in for an 02', but i would check that out at a local car audio shop, or best buy car audio.
i needed mine hardwired sine the wires in my dash were all messed up, and there was no stereo in it when i got it, but mines a 93 lol.
a simple harness for $20 should do it for you though, and then an adapter to make the new deck fit into the dash.
crutchfield will sell all this stuff.
anyway, the deck should be easy to get out. crutchfield might have info on how to take it out, or a hanes repair manual.
or you can buy something like this:
http://www.carstereoremoval.com/htm/stereoremovalFordExplorerSport01_03P.htm
anyway, once its out, you have the old deck out, and new deck in, you can start wiring the amp, which is really easy actually, it took me about 4 hrs for my first time, working at a casual pace.
basically all you do is mount the amp, then run the remote and rca wires from the deck to the amp.
run the power wire from the batter or other 12 volt source to the amp, and ground the amp well.
then run speaker wire to the sub, and your set.
that is a very simplified version of it.
but you can find tons of stuff online about amp installs, or if you want i can take some pics of mine and show you how i did it.
it should be easy to do, if you do a bit of research, and i will be glad to help you out if you need it.
riley