Puma gearbox dismantling

Has anyone taken apart a puma gearbox.
Mine is stuck in reverse and a forward gear. It also had a problem with the syncromesh in 2nd prior to this problem.
Chap who does my other gear boxes has got it out no problem but is struggling to get the box apart.
Does he need a special tool or is their something we don't know about?

Melt it down as you would cheese on toast and serve it with ketchup.

cream cheese isnt very nice grilled