I assume you talking about DRL lighting. No. That year Sable came with an automatic system which turn on all the lights when ambient light dropped and had a delay off timer when the car was switched off.
The brake lights on a 1998 Mercury Sable are changed by removing the retaining screws, pulling the light assembly away from the vehicle, and removing the bulb. A new bulb can then be installed and the assembly put back in place.