Motor mounts on a car rarely need service. It is possible, however, that they can deteriorate or crack over time, especially if a car like your Buick Park Avenue is an older model. The Park Avenue uses individual motor mounts that are connected to the supports at different ends of the engine compartment. You need to replace a damaged mount, quickly, to avoid engine strain on the chassis. You must also properly support the car, during the procedure, for the same reason.
Raise the front end of the care, and support it on jack stands.
Place a wood block or board on your floor jack, and raise it under the oil pan to slightly raise the engine.
Raise, and support, the engine further with an engine support fixture, which you may need to get from a rental yard. This device usually uses a combination of hooks and strut towers to support the motor.
Unfasten the engine mount that needs replacing, and disconnect it from the motor support bracket. Remove the mount bolts with your wrench, and remove it from the engine block.
Attach the replacement engine mount to the engine block, using the wrench, and connect the mount to the support bracket with the fasteners.
Lower, and carefully remove, the motor from the support fixture, and lower it off the jack stands, using the floor jack.
