Until you go through your guinea's first breeding season you don't know what guineas are really like. Unless you are NPIP certified and include the proper paperwork, it is not legal for you to mail Ralph any hatching eggs.
In addition, I am NPIP and cannot bring any birds into my flock that are not NPIP.
As far as hatching rates go I find guineas hatch at about the same rate as chickens.
Do not get me wrong, I love my guineas but I have no illusion as to their character.