Dont do it. Unless you are serious about it. You going to need one or two people that can help you out and you can trust. Also, its very important to be patient. Scope him out. Find out to see where lives and the places likes to go to. Once that's done, get at him and rob him.
But on the other hand. He knows where you and your folks stay, just in case he want to retaliate after you rob him. Think things through before acting out the task. A lot of people fail at that.
Instead of robbing him, knock his punk ass out for scamming you and leave.
P.S. Get your 55 bucks back.