Some of the other guys might be able to offer some better thoughts. I've seen a variety of prices mentioned on this site. I had mine done last year (at about 85,000 miles) because my water pump failed. Since it is a '99, and the water pump went, it was time to do it all even though it was well under 100,000 miles.
You will want to make sure you get the "whole" job done at the same time for cost efficiencies. That means you should look at replacing the following: timing belt and tensioners with pulley; water pump; drive belts (serpentine/AC); and radiator hoses. Assuming you are going to have the work done by someone, it should be somewhere between $600 and $1,200 (at a dealer?), When I had mine done, it was around $800.
Depending on where you live, one of the experts from this site might be nearby and could do it for you cheaper. Good luck!