ok phone around a few places that will recon a gearbox, let them know the issue it has, they can then give you a price for a replacement or to recon yours, you can then whip it off, get it done or swapped then refit, it is not really much of a job to do if you are reasonably competant
a couple of years ago my very reliable landrover steering box developed a seep leak....common problem i hasten to add
new one from landys was around 700 quid, phoned a recon place, removed it, posted to them via courrier, they recond it and sent it back by courrier, 150 quid plus 20 quid courrirererirrier. complete bargain
worth looking into as an option as there is not much to a gearbox really, plus might want to cx the clutch at the same time, if it is cheap enough then might be a consideration