You said you were new to cnc. Do you have a cnc yet? If not, take some time to research as many options as you can and study. I would suggest that probing is not necessary to model a guitar unless you are trying to replicate something exactly as in an antique or rare guitar. Otherwise, just model it in cad and machine it.
I would suggest you take a look at Rhino3d version4 if you want to do this type work because it is both a very accurate technical cad, but an excellent surface modeler as well. Madcam would be my choice for cam to get the gcodes from Rhino to your machine.
Mike
No greater love can a man have than this, that he give his life for a friend.