ok here are the two parts...
first the software that opens and transmits a gcode filehttp://www.mmcpix.com/CNC/CNCdriver.zip
you will need to click File :: Options to chose your COM port (and any other settings you fancy)
As well as sending the gcode it shows a picture of what it's up to
It's aimed at PCB milling btw
second the gcode interpreter that runs on the Unohttp://www.mmcpix.com/CNC/GCode_Interpreter.zip
DO look at _init.pde as you will need to configure it to suit your machine
It supports 3 axes each with limit switches
like I said I think it's idiot-proof, but...
feel free to ask questions, but I take no responsibility for you destroying your Arduino, drivers, motors, house, wife, children, sundry other loved ones or any other part of your immediate environment!
oh and if you make any changes - please let me know what you did
Do you have any info on the machanics of your build, btw?