There's a two writeup tutorial, On hack-a-day on how to solder it should teach you whatever you need to know about common ground controllers etc, If not shoryuken's Tech-Talk, Section has very large writeups on how to mod your controllers.
Ya know, speaking of that tutorial, I enjoyed it, and it is well within my level. I'd love to do it, but I have no access to a cnc machine, and would probably have to modify the design for a different moniter.
