The Nissan Xterra has the new halogen headlight bulb inserts. It's not like the old days when the sealed beam units were replaced. To gain access and room to the halogen headlights, it may appear at first that you'll need to have the motor lifted out of the engine compartment, but it's not quite that complicated. You might have to remove some components to get them out of the way, but you should be able to replace the headlight units in your Nissan Xterra without recruiting the help of an expensive mechanic.
Open the hood to the Xterra.
Determine which bulb needs to be replaced and what you're going to have to move to get to. For the passenger side, remove the battery bolt with the ratchet, extension and a socket. You won't have to remove the battery, but you will have to be able to move it around some to fit your hand in front of it. For the driver's side, you may have to move the air box cover by unclipping it.
Unplug the wire harness plugged into the back of the headlight unit. You will need to pull up on the locking tabs while pulling away from the headlight to release it.
Turn the metal retainer counterclockwise to release the headlight from the headlight assembly. Remove the headlight.
Place the new headlight into the retainer ring lining it up properly. Do not touch the glass bulb of the new halogen headlight because oils and alkaline in your skin can compromise the life of the bulb or damage it altogether.
Insert the headlight bulb into the headlight assembly and turn the retainer ring clockwise until it locks into place.
Plug the wire harness back into the plug of the headlight.
Test the lights by turning them on. Once you confirm that they word, you can replace the battery hold down bolt or air filter cover.
Remove the tools and old headlight and close the hood.
