Re: Newbie here
if it's like my '96 there are just two screws in the middle of the door, then take off the mounting plate that is around the door handle. then you pop out the little plastic 'screws' that are all around the outside of the door (there are probably 10 or so of them, you'll have to pull fairly hard but don't worry about breaking them, just pull evenly on either side). Then lift the whole door panel up to get it out of the window well. You'll then likely have to undo the wiring harness for the power locks and windows.
Getting the speakers out is no biggie, just have a couple screws. The speaker wires, as usual, are mounted to the speaker with a harness so you'll probably have to just cut the harness off. When I did it the color of the speaker wires in the door didn't match any that were behind the deck and I couldn't find any correct wiring diagrams online to match up the wires. So I decided to just run new wires (getting them through the doorjam is a big PITA), but I was going to anyways since I have all aftermarket stuff and all my speakers are amped.
the subwoofer I don't know about since mine doesn't come with it. Unfortunately, if you have a sub, I assume you have premium sound? You'll have to find the factory amplifiers and bypass them if you are putting in an aftermarket deck too.