Its not difficult at all to wire a PC. You can use either a AC to DC 12V transformer, a cell charger (as close as 12V the better) or a PC power supply. You just need to connect the + wire to the + terminal of the fan and the same with - wire and terminal.

But i wouldnt advice you to use PC fan if you are using ducts. PC fans gives very little static pressure, often to little to be able to pull or push through a duct keeping a decent airflow. If any, you need to connect two stacked fans in order to get enough pressure for the task. An exhaust bath ban is often an easier and better suited alternative, and that may be cheaper than the PC fans plus the transformer. Very often, bath fan with same CFM rating than a PC fan gives double the static pressure, due the larger thickness.

There are too axial fans (like PC ones) working from mains AC directly that are thicker than PC fans (38mm and still more), gives more static pressure and dont need wiring. But they are usually very noisy.