I'm running Tkinter on a machine that has 3 monitors.  Is there a way to specify which monitor (& the location on that monitor) to display my GUI?
The .geometry() method of the root (or any Toplevel) window is your interface to its size and position.  Call it with no parameters to get a geometry string; you can then call the method with that string to set the window to the same place on the screen.  For example, I get '200x200+5+28' for a small window on my main monitor, '200x200+2592+414' after moving it to the monitor on the right.  (This is on Mac OS X, conceivably it works differently on other platforms.)
Tkinter: Issue with Multiple Montiors