Iv never done one before but i think all you gotta do is remove the skidplates from underneith it and unbolt the cover, clean it up, throw another gasket up, and bolt her back down. (fill her up too of course)
He's actually talking about the driver's side axle seal. This is definitely much harder than the diff cover itself. I suggest taking it to someone who can do it for you. More expensive, but it'll be done right and much quicker.