You can replace engine mounts in about three hours with a moderate level of difficulty, according to Mobil Oil. Alternatively, a mechanic may charge between $200 and $500 to replace a motor mount, depending on the model of car.
To replace a motor mount, you need a floor jack, jack stands, blocks of wood, a ratchet and a socket set. As this repair requires raising the engine, first ensure the engine has space to move and that hoses and wires have enough slack to move without breaking. Place wood between the jack and the engine, and raise the jack just until it becomes tight against the engine.
For safety, place jack stands under the engine. Remove the bolts attaching the engine mount to the engine. Then, remove the bolts attaching the engine mounts to the car's frame. Using the jack, raise the engine until there is enough space to remove the engine mounts. Reset the jack stands to support the engine. Repeat this process in reverse to install new engine mounts.