I'm sure that you'll get all types of responses to this question. Here's mine. I had nearly 25 years of guitar building experience before I built my first cnc router. I built it primarily to ease the amount of arm use due to repetitive motion injury. It didn't take long for me to see that I could do other things that I never dreamed of. If you intend to build guitars for a living, CNC will be a benefit, but you really probably should know how to build a good guitar first without one, as the machine is just another tool in the arsenal that you can use to get you there a bit faster and perhaps more accurately.
Really, the CNC is best on multiple parts of the same kind when you factor in the time involved in drawing and tweaking of the programs you need. If you intend to make different guitars then you need different gcode for the different parts that you change. This will involve tweaking of both your drawing and perhaps the gcode to achieve it. You will need to learn skills to complete, finish, and set up the guitar. Current cnc machines and computers that you can afford can't subsitute for the human aspect of this part of the process although who is to say that 5 years down the road they won't be able to.
. Can you build a guitar without the knowledge of doing it by hand? Probably, but you might be surprised at how much you can learn by having someone with the background teach you how do it. If I had to do it again, I'd get the training and then some experience, and finally the cnc. YMMVMarty
Good luck with it all.