How do you change the motor mounts on a 1998 buick century?

General instructions for replacing motor mounts on ANY vehicle: Put a floor jack under the engine, distributing the weight evenly using a board or some other object, just take the weight from the motor mounts by jacking up the engine slightly. Loosten the nuts that hold the engine to the motor mounts, jack up the engine until you have an inch or two clearance. finish removing the motor mounts, then put the replacment motor mounts in the same place. Lower the engine back onto the motor mounts, but keep the weight off the motor mounts until you have put the nuts back in place. After everything is back in place, take the rest of the weight off the jack and you're done.