They are full time AWD, literally the exact same as a V8 4Runner, we average 14-16mpg mostly city driving, but with 265/70/17 tires so that hurts gearing a bit. And it's cold here 1/2 the year which doesn't help.

Toyota should be able to do the timing belt service with no issues, it's all the same under the hood.

'05+ gains vvti and a nice power increase, and there are several different versions of the factory nav through the years, they gained Bluetooth (calls only, no streaming) at some point, but otherwise they are pretty well the same from '03-'09.

Sport models got KDSS which improves handling on road, while allowing it to still flex offroad, I don't have this system so can't really comment on if it's worth holding out for.

'04+ gets the 5A tranny, so I'd skip the '03's for that reason.