If you are talking about replacing a low beam lamp, you already have projectors installed (2006+) and are perfectly capable of installing HID H11 lamps with ballasts. (just adjust the metal shield in the light housing to eliminate squirrel spotters and make sure your headlights are aimed correctly.)
if a fog light (9006), technically its a reflection housing and you shouldn't but alot of people do, if you choose to make sure to aim them down.
If a high beam (9005), I wouldn't recommend HIDs for this application, the ballasts don't like on off fast switch behavior. LED lamps are an option.