Don't read too much into my comments - while I have read about the RepRap, I haven't investigated its requirements in detail.

As far as microstepping is concerned, the combination of steps per revolution out of your motor and the pitch (turns per inch) of your leadscrew will determine the linear distance that your tool travels with each step, and so that needs to be coordinated with your intended application.

As far as the motor goes, 179 oz in is on the lower end of the motor rating range that I have seen people use with DIY CNC machines.