It is self aligning for the most part. The sleeve, shaft, ZF housing, and bolt need to be lined up and the bolt just goes into its threads in the ZF.
I checked with Wilkinson and he said the o-ring tends to fail and the seal is usually okay. I am going to try just the o-ring. If it still leaks I will replace the seal next time. This is an easy area to work on. Just do not drop the speedometer shaft into the transaxle, put vise grips on the flat tab.