Could I suggest that you try running LinuxCNC as a live install for a few learning sessions?This means that you won't be dealing with issues of hard drive partitioning or formatting and still get to explore the Linux environment.To begin with you need to tell your computer which order to seek a medium to boot from and there will be a key indicated during the boot sequence to take you to a screen where you will be able to select the boot medium.If you select the usb stick,it will bring up a menu that will include a live installation.After a few minutes you will have a working live installation to play with.
If,after a few trial sessions,you feel sufficiently comfortable to commit to an installation it isn't too hard to partition the hard drive to convert to a dual boot machine.If you don't intend to retain any of the old operating system,you just format the entire drive.You can do the latency test in the live installation but it maybe a more accurate outcome if you wait until the actual installation.The configuration for your actual machine isn't hugely difficult until you add in some of the nice accessories,such as ATC.