2003 timing belt

I was wondering if there is any other parts that I need to change besides the timing belt, water pump and tensinor's. for the 3.0 v6 in a 2003 sienna

While the water pumps today are quite reliable (as compared to years ago), a water pump job basically requires the whole timing belt job to be done in order to change it.
So, many change the water pump while they are right there.
I just had that done on my 2003, just short of the 90K mile timing belt service interval.......Both Belt and pump.....but not any bearings.
Turned out that the dealership was the cheapest......at just under $500.
The correct coolant to use, if you want to stay with OEM type coolant, is Toyota RED......it comes as a concentrate.......mix it with an equal part of distilled water to get a 50% mix.

The timing belt job on the 1MZFE motor is major labor........which is why it is kind of pricey.
It will take you a while to do, even if you are experienced.
Read the factory instructions before starting the job......to make sure that it is something that you are up to.