I replaced mine about two years ago. What a difference. The car handles much better off the line. This would also be a good time to drop the rear end and open the "hog's head" to check for wear, as well as replace the oil seals.
It also follows that if you have dropped the rear end, the drive shaft will be out, great time to check the u-joints. (make sure you mark the drive shaft and output shaft positions before removal)
Yes most of my $20 projects turn into $200 projects quickly.
Good Luck.