Helped a friend this spring do one.  Basically the color and stamp rental doubled the cost of the concrete.  We had one guy who knew what he was doing and a bunch of grunts.  Probably 4 people would have worked well for the area we did.  15x35 or so.  It's not rocket science, but needs to be done right.  He let it set way harder than I would have thought before we started the stamp, it turned out well.  Find someone that knows what they are doing and give them a couple hundred dollar bills for a Saturday morning side job is my opinion.  Ben