Like others have stated, there's a very steep learning curve, but it's well worth it, especially if you're doing production work.
When I first got into this, I was pretty overwhelmed, and I have a background and degree in 3D modeling, so don't feel bad about asking questions.
You found CNCZone which is a great resource, but it can be very overwhelming. Read everything you can, and learn whichever software you end up using as well as possible. Duh, I know, but there's always more than one way to do things, which few people actually move beyond.
As far as design software for a 1st timer like you asked, there's a bunch out there and none of it cheap (from what I've seen). I tried the Rhino3D (design) and RhinoCAM (NC code generation) demos and just couldn't deal with its maddening interface and UX, but it works for a lot of people. I've heard BOBCam is decent and not terribly expensive. Personally I use SolidWorks (design) and HSMWorks (NC Code), but that's serious overkill for just doing guitars.