The headlights in early models are replaceable sealed-beam units containing both high-beam and low-beam filaments; if one filament fails, the entire unit must be replaced. To replace the headlight unit, first remove the screws holding the decorative trim ring, taking care not to disturb the headlight adjusting screws. For rectangular headlight units, remove the four retaining ring screws, while for round units, loosen the retaining ring screws and rotate the ring counterclockwise to release it. Pull the headlight unit out enough to access the rear and disconnect the plug. Replace it with a new unit of the same size and type, ensuring proper alignment with the bucket. Install the retaining ring and trim ring if applicable. For halogen bulb headlights, ensure the headlamp switch is off, lift the hood, and locate the bulb at the rear of the headlamp body. Remove the bulb retaining ring by rotating it counterclockwise, then carefully pull the bulb straight out and unplug it from the electrical connector. Insert the new bulb without touching the glass, aligning the grooves in the base with the tabs in the socket, and secure it with the retaining ring. After installation, check for proper operation, noting that a properly aimed headlamp typically does not need re-aiming after bulb replacement. For headlight assembly replacement, remove the parking/turn/side indicator light assembly by unscrewing the upper screws and lower nuts, unplug the bulb connectors, and completely remove the assembly. Then, unsnap the upper headlight assembly retainers, turn the horizontal adjuster out of the adjusting nut, and remove the headlight assembly from the vehicle, reversing the process for installation. Proper adjustment of the headlight is necessary after installation.