The '01 Century is most probably the 4T65E, and has a PCS instead of a vacuum pressure modulator. The left cover needs to be removed to access the valve body and solenoids. That will require removal of the LF suspension including strut from the knuckle, removing the LH axle shaft, removal of the LF inner fender, and dropping the cradle sufficiently to access the pan. A Century is going to be more congested than a W body or Montana (like the original post), so it may also require removal of the ABS system module. A review of the transmission R&R procedure should offer greater detail.