Re-program focus button?

Thanks to all of you who helped me sort out my D600-D800-D4 buying issue.

Quick question to you knowledgeable folks.  Can I program any of these cameras to turn off focusing on a half-click of the shutter.  It seems that when I half-click and focus and then click to make the photo, the camera refocuses.  I've heard that you can program the AF-L button to be the focus button.  True?  How?

Thanks for your help as I've been a manual focus guy most of my life and its hard to break the habit.

--
John Santoro
San Francisco photographer
www.johnsantorophotography.com