Gear Box linkage ? Range rover p38 manual 2.5

Hi I purchased the car on Friday drove 820 miles to get on a ferry and just before I manage it there were no gears I was told by the recovery guy it was more than likely the gear linkage, he also said you did not need to drop the gear box as it could be got at from the top help if anyone one has done this or posted a video please let me know many thanks Chris