Thank you very much Andy for this complete and technical answer. As a pro, I have all the required equipment and can raise all what I want to !
Once the gearbox and extension shaft out, I'm not sure to get the engine out. Centralise the clutch is easy and should be a problem.
Anyway I will take care about all the watch points that you talked about and will let you know once the job done.
Thanks again
PS : sorry for this late reply but I thought that I would received an email once my post would got a reply...