Newer Haynes manuals are useless if you want to work on a gearbox, they basically say DONT!!! Which is far from helpful when you want to.
The Haynes Fiat 127 or 128 manuals have a good section on the gearbox in them. Although it is slightly different you still get the general idea. Of course the 1.4turbo has a whole new breed of gearbox so it might be completely different (I'm not sure).
I used the 127 manual when I rebuilt the box on my 1108 FIRE, was pretty accurate, it didnt show fifth gear but I worked that out OK. I just went to the local library, found the manual and photocopied the appropriate pages.
Once again I'm not sure about the turbo because its got the newer gearbox and I don’t know how different it is from the older one.
One final note, I think syncros are a bit expensive so it might be worthwhile just putting up with it or buying a working second-hand box. I did the dodgy and used the syncro from my old 4-speed box