Paul,
You can replace spark plugs yourself. Its pretty easy, if you have the right tools. The spark plugs are in the engine block, and are probably under a spark plug cover. Because you have a V6, you'll need 6 plugs. Look for 6 thick wires all going into the same little area on top of your engine. They probably all disappear under a plastic cover; this is your spark plug cover. Remove the cover, and you'll see your spark plug boots.

If you've never replaced spark plugs on any vehicle, I would highly recommend you buy a repair manual for your car. Most auto parts stores sell these manuals for around $15; both Haynes or Chiltons are good. You can get them at AutoZone, PepBoys, Advanced Auto, etc... The repair manual will walk you through step by step on replacing your spark plugs.

So, when you buy your new plugs, buy the manual and the special spark plug socket; if you don't already have one. You'll also need a spark plug gapper. None of these items are expensive. Once you do a spark plug replacement once, you'll know how to do one on pretty much any car.

Good luck!