A High Intensity Discharge lighting system is quite different than a simple bulb change.
HID uses a special power supply to produce high voltage pulses that ionize a gas inside the bulb envelope. This strobing effect is too rapid for the naked eye to notice, but it is a strobe effect and consumes less current than a continuously lighted bulb.
There are "kits" available but they're fairly expensive at about $400 - $500. They include a power pack, ballast and a different bulb. While expensive they do produce a lot brighter light and the bults should last longer due to not having a filament to burn out.