Land Rover Repair: Discovery Gear BOx, transmission problem, gear oil

Question
Sometimes I find it difficult to change gear, but other times its fine, do you think its the gear box or clutch that needs attention?

Answer
The symptom you describe could derive from either gear box or clutch failure.  Both components quite commonly do fail.  

To start with, make sure the oil in the gear box is a thin synthetic oil and not heavy gear oil.  Next, if you engage 1st or Reverse from a standstill and it crunches into gear, then you have a clutch problem.  If shifting up and down through gears whilst travelling it is a transmission problem.  If it does both, you have a problem with both components.