Hi Andy,
Good to see you jumping into the fray.
I checked out a bunch of the available plans for acoustics when I decided to build my "ideal" guitar. The Grellier has generally good reviews, but it didn't meet my specifications so I did my own CAD plan for what I wanted. I posted the PDF of my plan
HERE on the AGF for anyone to use.
The majority of free plans on the net will provide the basics of what you need, but the only way you really gain an intimate understanding of how the instrument works is by building a few times.
Fathand's comment on form depth is a good example. A new builder would think that you would want to fully support the sides, but that's not how it actually shakes out. Since you usually end up working on a protruding portion of the body, it ends up being counter-productive to have anything more than 3" of form depth. This is stuff you only find out by actually doing it.
You're off to a good start!