NEMA34 just gives you the size of the stepper motor - it doesn't tell what you the electrical specs are. You seem to be assuming that your stepper motor will come with an integral driver, and I don't know whether you have a specific motor in mind that has this, but they don't all have. If you get one with an integral driver then you just need to interface the Arduino to that and give it a suitable power supply. What that involves would depend on the specific controller being used. If you get one without a controller then you would need to provide an external driver with a suitable voltage and current rating. Again, the rating would depend on the spec of the motor but I'd expect it to need something of the order of 10-20 Watts of power - you can get motor drivers that cope with that sort of power, but not all do. You need to start with the electrical spec of the stepper motor, though, before you can define the requirements for the driver.