I'd also do some research in to the car you have to find out if they often have gearbox problems.
My car is prone to the gearbox shitting itself, so I'll be replacing with the correct factory spec'd oil when the time comes, in the hope to offset the inevitable for as long as possible.
Does expensive oil make a difference? I'm going to replace my gearbox oil. The recommended spec is 75W/90 GL4.