Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
I think it's an engine out and split the cases job to renew that oil seal.I'm sure the oil seal has outer ridge that locates into grooves on the cases, but somebody else will be along shortly to confirm or correct me on that.But you won't have to touch the top end to change that seal, just pull off the side casings and remove all the gubbins, then turn the engine upside down and spilt the cases, remove the cam chain tensioner so you can ease the crank up a bit to remove the seal.Any way good luck with that.Skoti