I wouldn't change anything, I'd go back to (negative) five years ago, find out who wins all the major Horse races, come back and chill for five years. Then do it all over again. Going back in time would only interest me if it was to see dinosaurs, or indian & pilgrims, especially, the indian days, pteradactyls, hipodermuses, midget monkeys, to see the formation of a volcano (in 5000000 x SUPER SPEED), or the formation of a river, or, better yet, a land of no vegetation.