How can I break a large granite rock into smaller pieces?

I have to put up a fence to keep my son out of my neighbors yard. I don't have many tools myself, but I have access to many. I can't spend more than $20 or so on a solution. There is a large granite rock right where one of the fence posts need to be placed. I've dug around the thing to see how big it is and realized there is no way I can move it. It's bigger than a beach ball, but smaller than one of those exercise balls. The guys at Lowe's told me to use the hammer drill that I already have and use a masonry bit for granite to drill multiple holes and than start whacking away with a sledgehammer. I bought the bit, came home and thought about it, and it seems like a bad idea to me. First off, I think I'll end up wearing out bits quickly, and secondly, I just don't think it's going to be that simple. Anyone have any better ideas?