Rob, There are some helpful software threads in CAD & CAM Software

and if you decide to use SketchUp, here are a few specific threads:

http://www.mycncuk.com/forums/cad-ca...iscussion.html
http://www.mycncuk.com/forums/cad-ca...omponents.html
http://www.mycncuk.com/forums/softwa...bam-mach3.html

Happy Learning-Curve..... Enjoy!

Cheers,
Andy