Using Arduino to control servo as a stepper

Hi - I want to use an Arduino Uno to control a motor as a precision stepper motor. I'd have input from sensors (still ordering and testing a few kinds, probably a pressure sensor) which would then control a motor which would push a part through a step of a manufacturing process. I took a class using Arduinos in college last spring but all of the hardware was assembled for us and we focused more on the programming aspect of the project. I don't quite know what sort of hardware I need with my Uno.

My idea was to connect the motor to a power supply and have the Arduino control when it is on and when it is off. This control would be governed by the read of the sensors, but like I said, I'm completely clueless as to the hardware setup I would need to make this work.

Thanks so much!

The terms 'motor', 'servo', 'stepper motor' mean different things. I suggest you consult Google to understand the difference, decide which of those you actually want - then choose the appropriate hardware.