Well, you should start by getting your hands on a Chilton's or Hane's book for your car. I would imagine you have a transverse mounted V6, with 3 spark plugs on the front of the engine and 3 on the back. Your owners manual (if you don't have the Chiltons) will tell you what plugs you need, or the person at the parts counter can help you.
Just follow the plug wires to each spark plug, pull the wire off the top of the plug. Slide your socket down over the plug and remove it the same way you would remove a bolt. After checking the new plug for the correct gap, insert it into the hole (use your fingers at first to prevent cross-threading) and tighten it with the socket. Do them one at a time to prevent connecting your wires to the wrong plug.
The back ones will be trickier to get to, and you may end up taking it to a shop where someone with the right tools can do the job faster and easier than you can.