A warning. That pivot shaft can be a bear to remove and install. It frequently ends up damaged in the process as it is a soft metal. There are 4 o-rings associated with this. They are dust protection for the bushings and are not essential. With your axle out, it is easy to check for wear on the shaft bushings by checking for excessive loosness between the halves of the housing. If the car had regular care and grease, these bushing do not wear out. I do strongly suggest, that if these bushings show little wear, do not remove that shaft. You are better off to leave it alone. Do change the axle boot. The split type boot works very well and with your axle out, it is easy to replace.