Got a leaky gearbox on my uk2000 turbo coming from the front drivers side drive shaft, is it possible to change the seal without dropping the gearbox out? Or will it need refurbing/replacing etc. How difficult is it to change or rebuild if I went down the DIY route? If worst comes to worst where’s the best place to get it refurbed or get a refurbed gearbox? Any help much appreciated.

If it's just the inner driveshaft seal , they're about £15 for a genuine seal and they just pry out and tap back in (gently).

You'll have to split the bottom balljoint and track rod end that side , remove the split pin in the inner c.v and swing the front leg out with the drive shaft attached. 

You'll need to refresh the gearbox fluid as it will leak out when you remove the seal from the gearbox stub axle. 

As for a more major damage ,any second hand 5 speed with the same ratio as your existing box , will fit and would be cheaper than a rebuild .