A dealership is the worst kind of PO... They have all sorts of nasty tricks not available to your average PO to deceive you into thinking the car is in better shape than it is. You can't see the timing belt without partial disassembly of the engine, and no dealership is going to spend that kind of effort on a car they're trying to flip quickly for a profit.
Toyota has a site (someone else will have to reference it, as I've only ever had one car that could have possibly qualified) that will give you service records IF the services were done by the dealer AND the dealer was together enough to record it. Aside from that, I'll reiterate: make no assumptions.
Christo Slee told me something that I really appreciate (I'll have to paraphrase this one). The reliability of a Toyota is both a blessing and a curse. If you take care of it and provide it with all necessary care and feeding you can get hundreds and thousands of miles out of them. The problem is that they're so damn reliable that the non-enthusiasts don't know HOW to provide proper care and feeding, and thus don't bother unless some genuine can't-ignore-it problem surfaces (at which point, it's too late). A new Sequoia is a Class A soccer mom mobile, and soccer moms are about as far from enthusiasts as you can get. If it doesn't have a glaring problem, it's probably not going to be addressed. Timing belts don't slowly go bad; they die hard, fast, and in a spectacular and expensive fashion. It has an interference engine and hasn't been totalled, ergo, the timing belt hasn't let go. Assume it needs to be replaced, and save yourself the hassle of finding a rolled donor for the engine and have it replaced. That's the sort of thing you bake into the price of a used car when shopping.
Aside from that, check fluids, tires, brakes, shocks, plugs, etc. Anything that might be considered a wear item. Be glad it's a new enough vehicle that you don't have to count wire insulation and every single moving, electrical, rubber, or otherwise oxidable part and every gasket, seal, brush, blade, or sweeper to that list (the old ones are so much more fun!)