If you have looked at the thread above you should know whether it's the bulb or the ballast.
This link is embedded in the same link but hard to find..........
Shows you how to remove the bumper to replace the bulbs and ballast.
As long as the headlights are switched off or the battery disconnected there is no danger in doing the job yourself, the danger comes from the ballast which genarates around 30000 volts to light the xenon bulbs.
There is a wire that goes from the HID ballast and connects to the side light, if this is not connected the xenon bulb on the same side does not light up.