I hatched guinea eggs last year with a hatch rate of 5 out of 8 from ebay eggs, which ain't bad. Be forwarned, they're eggs are thicker than chicken eggs. I believe I helped all but one.
There's a great book called Gardening with Guineas that is a must read, as well as a forum for guinea owners called the guinea fowl message board. Its loaded with info but not as organized as this forum.