For 1999 DeVille cars, you need to remove airbags from work. When you need space to work, lift up the front of the vehicle and secure it on jackstands. After that, raise the hood. Remove the air deflector. At the front wheel area, remove the cover holding the splash guard to the bumper, and unhook any attachment screws that hold the bumper inner fender extension panels in place. If your car has these lights, disconnect the wiring that connects them to the electrical system. Take out all fasteners, split apart the bumper cover from its attachments, tug gently pulling the whole bumper away from the car's body. Under the car's front side, take off all the high-strength bolts and nuts that attach the bumper to the energy absorbers. To get enough clearance, apply the parking brake, raise the back of the vehicle, put it on secure jackstands, take the rear wheels off. The first step is to expose the nuts on the bumper cover and take out the ones holding the trunk finishing panels. When you reach the wheel wells, first take out all the bolts keeping the bumper connected to the body. Unscrew the bumper's mounting nuts under the car, then gently pull the bumper section clear of the body by pushing straight out and pushing forward. To put the bumper back on is the same thing as taking it off, whether you're doing it to the front or back parts.