Brake system problem; Vacuum booster, and/ or piston?

My old horse
(1st Gen,Taco, base dbl cab, 4x4 with 467,000 miles)
has developed 2 brake problems:
1. There is a clunky movement to the pedal, that I have heard might be the piston, and
2. a sporadic -sometimes almost failure- of the brakes. I guess I need a vacuum booster, and. Piston? IDK…

(Btw, I went with 17” wheels on this)

Any input on what ALL to buy before dropping it off at my mechanic, would be greatly appreciated!
My mechanic will work fairly cheap, but I need to bring ALL parts needed with me, or it adds a day or two (or Three) of time, since he’s stacked up.
—Btw, I know it’s in a different thread, but- going with the Tundra brakes mod, is not out of the question. For my year/Make/model, what parts do I need, and/or what fits this one?
Thanks in advance for anyone who can help with my shopping list!