Since you drew that guitar up there with details like fretboard with overhangs and the strings running tangentially to the tuner posts, I guess you have enough skill already to draw out a guitar. Do a couple more with the string thickness in the equation, and you'll get better + faster. In CAD, accurately drawing out the neck with the proper string thickness, spacing, overhang dimension and final nut width is a bit of work to do right, but is the most important part. The body shape, on the other hand, is something that is more design oriented and using a sketch approach on butcher paper to design that will probably work better for you.