Try EMC2 before you install.

http://www.linuxcnc.org/

The EMC2 team now has a custom Live-CD based on Ubuntu 6.06 that will let you try out EMC2 before installing, and it's also the easiest way to install Ubuntu and EMC2 together

I am very impressed with EMC2 - have used it for a year or so on a gantry and hope to retro fit a large horizontal mill next.

I'm still geeking out about it!

sam