Rear Differential Input Shaft Seal Replacement

Fred Munro has written an excellent DIY on replacing the left and right diff output shaft seals.
(http://12v.org/urs/FredMsAudiUrS4RearDifferentialRight&LeftSealDIY.pdf).

Recently, somebody on quattroworld asked about changing the input shaft seal, i.e. item 23 in this
diagram: http://12v.org/urs/RearDiffGearsWithInputShaftPN.jpg

The Bentley shows fewer parts than the above diagram and no Item 19 lock ring. It seems to show pulling the Item 6 cover and the Item 25 flange shaft. It shows the Item 22 round seal (O-ring?) but
does not show the Item 23 radial shaft seal.

Anybody with any BTDT experience on replacing the Item 23 radial shaft seal.

TIA

Dave F.