I did my V model in the free version of Sketchup. The "Sandbox" texturing tools only come with the retail version, and they would be really handy for all the curves, reliefs & angles on guitars.
It was my first ever 3D model of anything so it took a while, but with patience it can be done. Individual pieces of hardware (tuning posts, nut, trem, knobs, switches, fretboard etc) were designed as seperate components, all added to the main body. Mine is only roughly to scale +/- 2mm , it struggles with exact measurements.
There are limitations i.e. I can't find a way to properly shape the neck/body join & heel - but for a visualisation tool it rocks
http://i63.photobucket.com/albums/h130/thr.../Flying_G/4.jpg
http://i63.photobucket.com/albums/h130/thr.../Flying_G/3.jpg
http://i63.photobucket.com/albums/h130/thr.../Flying_G/2.jpg
http://i63.photobucket.com/albums/h130/thr.../Flying_G/5.jpg