Yes, you should replace them.
I am fairly certain your car came with standard NGK copper plugs....BKR5E-11's to be exact. The 2000's or the 01's came with platinum plugs.
Plats don't burn as well as coppers, but the plats last longer. If you're not in it for performance, but rather reliabiliy, you could get some NGK platinums and not have to mess with them again for at least another 60,000 miles....
If you look to your right, on the screen, there is an add for Club Plug. A set of stock plugs might cost you $10 shipped to your house. You could also go to a local parts store and buy them...I have a problem finding NGK plugs at local stores, so I always order them. Platinums will cost a few dollars more...but not too much more. You could buy Bosch in a pinch, but the general opinion on here is to stick with NGK.
Then you'll need a socket wrench, a socket extension, and a spark plug socket....oh, and about 10 minutes of your life.
Remove the old plugs, do them one at a time if you're concerned about mixing up the spark plug boots, and then replace it with a fresh new one. They come pre gapped, so no work is needed there. Plugs torque to around 28 foot pounds. If you don't have a torque wrench, just tighten until they are snug. 28 ft/lbs is not a ton, so don't go wild. You're threading into aluminum remember.
When you're done, you should have a pocketfull of money you saved, and you can go back to the dealership and give them the finger.