heres a site that has some of the build in a generic way... http://buildyourcnc.com/default.aspx basicly, once you get your cnc router built, with controller boards and motors, you use one of the many programs to run your files, i use mach3 ( nice and easy, but $159)
or you can use emc or turbo.
best way ( at least for me,) is to wade in and start swinging.
i have built 2 that way, and working on a third each progressivly bigger.
so my sign making path goes...
and then sometimes all the way back to turbocad to redraw, till it's just right
but once your done, that program is good.
hope this helps