[Greenie]

Personally I would address the timing belt and serpentine belt service first and foremost since you're right on the time interval on the timing belt at seven years (84 months). Better safe than sorry.

If you have the timing belt replaced it's only practical to replace the serpentine belt and avoid labor since this belt has to come off anyway to access the timing belt. While you're at it, an examination of the water pump, cam seals and other serviceable items would be wise. Once you've recovered from this expense move on to the transmission.

Has your transmission been serviced before by Toyota? If not I would have Toyota do it since R&R of the pan and cleaning the screen is a major DIY task. Then later you can do your own drains and refills or do the flush as outlined in several older threads on the subject.

I've performed the flush twice already on my 2001 and it's not rocket science. Just pay attention to details. I highly recommend synthetic ATF if you do the flush.

Best of luck on keeping the Tundra rolling.