GRBL is capable of doing 3D work. I'm using an old Raspberry Pi 2 to feed the GCode to GRBL and it's working fine. The limiting factor is your CAM software.
There's plenty of tutorial on YouTube about Fusion 360. Can be time ocnsuming if you're starting with no CAD knowledge.
The CAM part of Fusion is really easy once you have your part. Fusion can easily import 3d parts from other CAD package.
A little update on my guitar project. I've put all the coats of lacquer on it that I need. Lacquer is well cured and ready for wet sanding. CNC'd the neck and truss rod channel and the truss rod is installed. I hope to cut fret slots this weekend and glue on the fretboard. I'm still deciding on whether or not to add a pick guard. Not sure I want to cover up that beautiful wood grain.
I'm at it again building a new guitar. I've been learning how to do (hack) 3D in Fusion 360 and this neck is the result. I'm still working on perfecting the process and constructing the necessary jigs. The wood is red oak.
Just saw your thread.... very nice work you have done.