With these method by action directions you Testament grasp exchange the headlights on a 2004 Trailblazer.
1. First face the vehicle so the battery in on the right.
Second open hood.
Third Remove the Grill by pushing firmly on two retainer clips that are on the top, use the wide slot screwdriver to get the rest of the clips off. Pull up gently on the grill it should then pop out. The grill extends under each headlight assembly any other retainer clips should release when the grill in popped out.
2. Finally at the back of the headlight assembly you will see two rubber caps one for low beam and one for high beam, the white base is for the low beam and the black base is for the high beam. Unsnap the wire harness from the bulb base, turn the bulb clockwise.Replace the bulbs high beam on the outside and low beam on the inside.
Fourth on top of the headlight assembly you will see one 1" tab on the right and left side, pull the tabs upward about two inches and this should release the headlight assembly. You then should be able to pull the headlight assembly out toward you.3.