My linux -fu weakness was overcome with a change to GRBLweb - http://xyzbots.com/grblweb.html - they had a ready made image i was able to flash to my pi and now it works.
I then found out that getting grbl to think its moving 1 mm and actually move 1 mm is a little more difficult than i originally thought. after running around the shapeoko forums looking for help, i found this very cool website - http://homepage.ntlworld.com/r.j.noble/ShapeOko/grblcalc/ - and it was very helpful in getting my grbl settings dialed in.
So it's now dialed in. Now onto the calibration job!