I want to replace the headlight and the owners

look in owner manual you have to open hood. the headlight housing is held in place by push pins and two mounting screws.

is the check engine light on now,but it not showing. you have to remove the insturment cluster. there is four screws holding the cluster in

HEADLIGHT REMOVAL AND INSTALLATION
SEALED BEAM HEADLIGHTS REMOVAL 1 When replacing the headlight,do not turn the spring-loaded adjusting screws or the headlight aim will be changed 2. Remove the cover over the headlight this vehicle has five screws securing the cover other models may have four or six screws. 3. Remove the four screws which secure the retaining ring around the headlight support the headlight as this is done. 4. Pull the light away, unplug the connector and remove it from the vehicle. INSTALLATION 5. Position the new unit close enough to connect the wires. Make sure the numbers molded into the lens are at the top. 6. Install the retaining ring and mounting screws. 7. Install the plastic cover to the headlights with the screws you took off and check for proper operation. If the adjusting screws (spring - loaded adjusting screws) were not turned, the headlight should not require adjustment.

Open your tailgate. You will see the screws that hold the taillight assembly to the body. After the screws are removed, you may have to pry the light assembly GENTLY rearward to get the pins to release from the outside edge of the lamp assembly. Once the taillight assembly is out, you will see where the bulbs go.

To replace the headlights, you must first remove the trim ring around the headlight. There should be three or four screws holding it in place. Once the trim ring is removed, there will be four screws, two at the top and two on the bottom. Carefully remove screws and remove the retaining ring. Gently pull bulb out, unplug the wire connector. With new bulb in hand, carefully connect the wiring to back of bulb and carefully set in place. While holding the bulb in place, set retaining ring back in place over bulb and insert screws. Then replace the trim ring, tighten the screws and you are done.

The bulb or the whole assembly...?

here's a link to another fixya question/answer with the whole procedure and pictures for changing the headlight bulb.

http://www.fixya.com/cars/t2735420-replace_headlight


Also, here's a PDF owners manual for the 1998 Ford Explorer... and on Page 187 the headlamp stuff starts to get addressed.
http://www.motorcraftservice.com/pubs/content/~WOWEXP/~MUS~LEN/42/98expog1e.pdf

My 1992 Buick century headlights were not working so I replaced the relay now when I turn the knew switch on it takes a minute to 5 min before lights turn on

If its just the bulb you can untwist from inside under hood and replace. If the whole light assembley needs to be changed I am pretty sure it is just like my 98 3500. Lift the hood and remove the screws holding the grill on, then at the bottom of the grill there are screws as well , if I am remembering right I removed my parking lights also. Then the whole grill just pops off, remove screws holding light assembley and replace. Its really easy just take your time and get all the screws out, DON"T snatch on the grill, it will come off easy once you get the all

THE TOP SCREWS ARE EASY. THEN THERES THE BOTTOM OF THE GRILL. REMOVE PARKING LIGHTS. THERE ARE 3 PLACES AT THE BOTTOM OF THE GRILL THAT HOLD IT. THERE ARE NO SCREWS OR BOLTS TO REMOVE. JUST 3 PLACES WITH PUSH BRACKETS. LEFT, RIGHT AND CENTER,,A LITTLE TRICKY BUT DONT GIVE UP. LIFT AND PULL THESE TABS/BRACKETS. THE BOTTOM CHROME SHOULD COME OUT A TAB AT A TIME. YOU WILL DO GOOD,,,,RIGHT? YES

theres four screws that hold it in. alldata calls for .5 to replace so it shoud be easy good luck