If your truck already had a lightbar installed, you should have wiring at the base of the headache rack already. You should have everything there that you need. Like the other posters have said, figure out what wires do what, and then hook them into the existing wiring.
Stationary pylon all the way. The biggest advantage is that the lightbar stays pointing where it is supposed to. The second you tilt your bed with a bed-mounted pylon, the lightbar becomes worthless. Doesn't matter if it is blocked or not, since all the light is directed toward the ground and the sky. You do gain a little bed space, but the lighting aspect is the most important.