Last year I made a kit that was 3 years old. It had been stored well, and the wine is aging nicely.
I concur with the previous advice -- check the juice/concentrate, if it smells good it's worth trying. If your garage doesn't get roastingly hot, it's likely the kit is fine. The resulting wine may be darker than you expect, but that is only an aesthetics problem.
As far as I know, bentonite does not have a shelf life, so it is safe to use. Sorbate and yeast DEFINITELY have a shelf life, replace them. Not sure about the sulfite, but for the minor cost, throw out what came in the kit and use fresh.