Toyota Repair: 2000 Tundra 4x2, mile intervals, light loads

Question
Is the following service premature? I had my Tundra at a local dealership today to alleviate a check engine light. That was an O2 sensor issue and was repaired. The assistant service manager indicated that I should have the drive belt replaced due to cracking. I was intending to have that done soon anyway because I can see that it is wearing. She then went on and suggested that the timing belt be replaced along with the water pump (since it is accessible when replacing the timing belt). I am the original owner of this vehicle and it has been regularly serviced at this dealership for the past 7 years. I change the engine oil every 3,000 miles. It has an 8 cylinder engine with 72,000 miles. I have never towed with this truck and primarily use it for light loads and going to work. It is an automatic transmission. Should I have the timing belt replaced and if so should I have the water pump replaced? Thank you.

Answer
The timing belt should be replaced either at six year or 90,000 mile intervals, so it should be done soon, it's adviseable to replace the water pump at the same time because of mileage concerns, if the water pump is not replaced and should fail later then everything will have to be taken apart again to replace the pump.