Hi Herbert,
I did this job the last year....the only suggestion I can tell you is to remove the  gearbox with the  the vetus coupling installed (just dismount the fixings on the flange on the engine); in this way you can easily remove the axle on a bench because the space to work with the engine installed is very unconfortable. In fact also if you want to use an extractor (I did one with long arms) you have to pull the engine back to have a little bit of room....anyway you have to use not gentle manners to have a good results...but is better to work on a bench that in the engine compartment...in this way you can also change the  seal of the gearbox easily once removed the little shaft.
Just for your use i attach a pdf in which there is an explanation of the job....but I prefer to put the gearbox out of the boat with the shaft attached and to do the job in a confortable and safe way...
regards
Michele