Brownells can sell you the parts which are available. I don't think the hammer is one.
I polished mine and used the wilson spring kit. They worked fine.
I reccomend you get a set of springs and plungers for the trigger assembly prior to teardown as they love to run away and hide. Brownell can sell you those also.
I typicaly shoot mine double action so haven't noticed any problem with the hammer attacking my thumb.