If your gonna do the cover and you have time remove the cover and let it drain over night. Clean it like mad with brake clean b4 applying gasket silicone. Any oil will cause it to leak after. It's also a good chance to clean out the inside of the casing. No matter how often you change it there is going to be some build up inside of fillings. Also make sure the fluid you use has LSD additive or you can add that seperatly. Makes a
huge difference in operation. Change the imput and output seals if you have time cause it's a pain doing them later.