gcode file probably won't do you any good - what you actually need is an x3g file.
Basically makerbot designed an open source printer then made sure it could only be used with their own software.

Your best bet is either makerware(you need an early version - the current one won't talk to the older printers) or flashprint and choose the rep pro option.
links here: http://3dprintboard.com/showthread.p...ilable-slicers