Ok seeing as this stuff comes up pretty frequently, and I'm bored on a Saturday night I figure I'll write it because it comes up way to often. (I'll do pictures later..just because people can never seem to find what you tell them..

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Ok first, starting off with removing the old stereo. The trim around the stereo needs to come out first. Pull the ash tray out, and remove the 4 screws. Two right above the heat vents and two around the area under the ash tray. Next pull the shift boot (or if your in a auto pull the plastic part that goes around that). Once those are done, you should be able to start pulling the trim away. Sometimes the heater vents get stuck, so just put pressure on them and they'll stay put. Reach behind the trim and unplug the wires (should be 2 for the cig lighter, then 2 or 3 plugs depending on what model you have..hazard/defroster). Once those are all removed pull the trim out. The stereo has 4 screws holding the radio in...remove them and the stereo will slide right out. The brackets on the stock stereo should be put onto the new head unit, so it can screw right back into place. Install head unit and put everything back in reverse order!
Next, the door panels, seeing as this comes up pretty often to. Start off by removing ALL the screws that go around the door. If the door has never been taken off, there will be little plastic caps over the screws..pop those off. The door handle has 4 screws, two are hidden by small plastic peices and another 2 that you should be able to feel with your fingers..they're kinda at a weird angle. Remove those and pull that handle off..it comes out in two peices (be careful..they break easy). Next, the door handle thing (the thing you pull to open the door..whatever it's called) hold it open and take a flathead and pop off the plastic peice behind it. On the top right hand of the door, where the seat belt is, there's another small peice of plastic that the seatbelt is going through. There should be two push tabs, just pull those out. Last part is also the biggest pain..the window crank. What you havta do is use eitha 2 flatheads or a flathead and a SMALL pair of needle nose plyers. Use one flathead to pull the crank out far enough to see inside it, then use the other screwdriver/plyers to pull the metal pin out. They can take some time to get out, and the crank's break easy. Once you get it off, put it back onto the crank so you don't loose it. Take the door panel twords the bottom and pull it twords yourself and up. It hasta clear the window crank to be able to slide off. That's it..once it's off you should see the speakers right in front of you!
Now, the rears. These are simple as hell to do. If you don't have a spoiler light, the brake light just pops off..just use pressure. Clear your trunk out so you have space to lie in. Take a pair of needle nosed plyers and pop out all the small plastic clips that you can see poking through underneath where the speakers are. These tend to go flying everywhere in your car, so a good idea is to take a towel or something and lay it over the whole rear shelf, so when they pop up they barely move. There's maybe 8 of these...I forget and I aint going to look right now. Then, there's three of these that screw in, they're the larger ones with a slit in the top. You can use a flathead screwdrivers or your fingers..just keep turning them till you can pull them out. Once your sure everything is out, pull your back seat back a little bit, while tugging on the speaker cover rack thing..technical I know. Pulling the seat back a inch just helps it slide out smoother. Once that's out, the speakers are right in front of you. The rear screws on each speaker are a PITA to get to, so I suggest having one of those SMALL philips screw drivers to get them..that's the easiest way.
Now for the amp. There should be a few rubber gromets aroung your engine bay. The one I find easiest is the speedometer gromet. If you pull it back a bit, then lie down and look up around the area above the pedals, you can see light..that's where the wires are going to go through. You can cut the grommet to fit the wire, or just not use it, do whatever you want. Make sure to not have the +12v wire connected to the battery while doing this, or you'll prolly short it out and startle the hell outta yourself. Once it's fished through the firewall, decide which side you want to run it. I usually run it on my drivers side..because it's right there. All the plastic peices can be pulled up enough to allow the wire to be fished under. Right beside the drivers seat, you can pull up the plastic strip where the door meets, and get good access to the rug from there. I run it under there. Once you figure out where you want to run it, pull the back seat..only the bottom. There are two small tabs that you have to pull on, which are at the bottom of the seat facing the front of the car. Pull both these out and and the seat just comes right out. Fish the wire through the carpet and into the trunk. Since you got it all ripped apart, run the remote and RCAs..make sure to run the RCA's on the opposite side of the 12v wire, or you'll get a hum in your stereo. Finding a ground in the trunk shouldn't be a problem..there's plenty. People, feel free to add to it, I'm sure I forgot small parts here and there..it's just a quick go through to help out

Good luck!