If you're working on a Pathfinder model, remove the headlight housing. If you're working on a Frontier or Xterra, unplug the electrical connector. Remove the rubber boot if equipped. On 1998 and earlier Pathfinder models, rotate the plastic retaining ring counterclockwise until loose, then withdraw the bulb from the housing. On all other models detach the retaining clip and withdraw the bulb from the housing. Unplug the electrical connector, detach the retaining clip, then pull out the headlight bulb. Without touching the glass with your bare fingers, insert the new bulb assembly into the headlight housing and secure it with the retaining ring or clip. If you're working on a Pathfinder, install the headlight housing. Plug in the electrical connector and install the rubber boot if equipped. Test headlight operation, then close the hood.