If you have one ball left and the eight ball and you hit the eight ball into your ball and they both go in do you still win?

No, the 8 ball must be potted on it's own, potting it with another ball is a foul.

ADD: Technically correct, but not complete...potting it with another ball is a foul, but as the rules state, pocketing the 8 ball on a foul is loss of game.