That stepper motor is rated for 3.5A per phase, which is much higher than any of our dedicated stepper motor drivers can handle. You might be able to get that kind of current using a dual channel DC motor driver to control each stepper motor, but that has disadvantages too (e.g. doing this typically lacks useful features like current limiting and requires more complicated code to control).
What you choose for a power supply might depend on what driver you end up using, so I do not have a specific recommendation. However, 12 of those motors will require significant power, so one option might be to separate the 12 stepper motors into separate banks and power each bank separately.
How difficult it is to acheive a system like this is subjective, but it does sound like an abitious project. I suggest starting off by trying to get 1 stepper motor working how you want, then expanding on it as you go.
Brandon