Hello, I am trying to fix the 600 diesel engine rover that my father had before, and the problem it has is in the gearbox, I want to take it out and see where the problem is, but for that I must disassemble it and I have neither planes nor schemes or anything

. That's why I ask you that if anyone could give me a hand, passing some manual or something, at least the gearbox, I would appreciate it
a great greeting and thank you.