Gecko drives

I'm new to this whole CNC thing and have a couple of questions for
those of you who know what your doing.
I am planning to retro a mill drill using Gecko stepper drives, NEMA
34 600-800 motors. Will I be able to control these drivers from the
parallel port of my computer using Kellycam or some other program??.
Also I dont think I understand the Idea of powering stepper motors
with more voltage than thier nameplate rating, could someone clear
the mud for me?
Thanks for your help!!