They are under the engine cover. You need to remove all the ignition coils also.
The plugs are iridium and they are good for 100K miles.
When you remove any fasteners marked with blue or green paint, they can not be reused, only replaced. The torque is extremely important on aluminum bolts.
Better if you know exactly what you doing on these engine, otherwise it will cost you a great amount of money to repair.
You can find great repair manuals with step-by-step instructions, diagrams, parts locations and other important information here: http://bit.ly/mitchell_repair_manuals_online