In my personal opinion its all a judgement call. Some people will tell you to replace only the belts and some will tell you to replace the pump as well. If you have never replaced the waterpump, I would replace it with the belts as well as the idler pulleys. In this way, you can save yourself some labour costs if, for instance, 10k down the road your waterpump goes. The key is to find out if it has ever been replaced. If i'm not mistaken, your car originally came with a waterpump with plastic empeller(sp??), which in most cases was replaced under warranty period with a more durable one with a metal empeller.
I'm just a crazy m*thrf*cker, livin it up, not givin a f*ck, living life in the fast lane