Hi Henry,
I wish you good luck with your intentions.
I do have the same model as you but a bit newer - SE 2007 - and with a very good XF gearbox, which I do like, and being somewhat older than you I do not want to change it.
My first car was a Triumph Herald in 1965 when I was 31 and I do have some experience with mechanics, but 30 years of company cars when any work had to be done by main dealers means that I now know very little about the technical side of a car.
I wanted ands type when I saw a friend restoring a Mark1 in 1963 but I had to wait until 2013 before I got the cat I now have.
The 3 speed gearbox with double declutching meant that I looked forward to synchromesh and then the first auto box in 2001 [4 speed].
So now a mechanic does all my work!
Again, good luck, and keep us informed,
Regards,
Peter.