[s-cars] Rear Diff Input Shaft seal replacement

[David Forgie]

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.  (Don't make me
 take my spare Torsen diff apart just to find this out!!) ;>)

TIA

Dave F.