your 2000 ES is an "interference" engine meaning that damage could/will occur the timing belt break while the engine is running.
keep in mind, that the maintanence schedule is suggested by the manufacturer, you are free to perform any of these services when you see fit. You can pay them now or you can pay them later. :whistles:
Personally I would shop around and find the best price. When my 02 hits 90k I will go for broke and do the water pump, pulleys, tensioner, thermostat, seals and TB. I have got a good inde up here who is lexus and toyota certified. Check out Toyota service centers as well as independents and Lexus. Shop around, this is a steep one.
steviej