Just making sure you know how to choose fuses and wire gauges.
Go download the FSM from zeroyon.com. Look in the Engine Control (EC) section for Cooling Fan control.
The S14 uses 2 relays to operate the fan on either Hi, Lo, or Off. Relay #2 controls the Lo signal. Relay #1 controls the Hi signal.
If you just want your fan to operate like stock, then you don't have to cut any relay. Just wire the fan to the stock fan harness. Brown with White stripe for Lo, White with Red stripe for high, and Black for ground (you should only need one of these for your fan to ground). Or you can just ground your fan on the body somewhere.
The reason people cut the relay is to operate the fan on Lo all the time, unless you get a Hi signal. Then it operates on Hi. But all other times, it just operates on Lo. So the ECU is really only controlling Hi operation.
The ECU controls the relay by providing a ground signal and completing the circuit for the appropriate relay. The relay then routes power through to the fan to the appropriate Hi/Lo terminal.
By grounding out the Blue with Green stripe wire going to the #2 relay, you're essentially tricking the fan into thinking that the ECU is always sending it a Lo signal.
In the FSM, the #2 relay is labelled E1. It's in this picture:
Here's a pix from the FSM to help you find the location of the E1 relay in the fuse box.
That should answer all your questions. I would also advise you to be extremely careful when working with the relay because it's easy to damage the harness.
Good luck, and post up any more questions if you have them.