The diff is pretty straight forward. 3 srews an WALAA its apart. As long as you have it apart I would clean out the bearings check that the
diff turns smooth. Listen to it if you hear crunching or grinding take the whole diff apart and rebuild it. I would wipe out all of the old grease from the diff and put some new grase in. Don't over fill the case with grease just a good coating on the diff and some on the inside of the housing. To much grease can heat up the diff and ruin it. After you clean the bearings lightly oil them and reassemble. While you have the diff case apart clean the out side with a soft bristle toothbrush and some WD 40 it will make your case look like brand new.