I've got a bit of an oil leak on the gearbox nose cone and drive shaft seals. Can these be changed with the gearbox left in and how easy is it? This is on a recon box!! But that's another story involving one of the big companies who advertise in all the UK vw mags!
Nose cone seal is a lip seal that is easy to replace with gearbox out and the nose cone off and the hockey stick out. You cannot do it with the gearbox in. It is impossible to reach over the torsion bar tube. The drive shaft seals can be done with the gearbox in but its easier with it out lying on its side. The major challenge there is undoing the bearing carrier with either a special spanner or creativity to get at the seal.
Mike, you do not have to touch the bearing carrier, the main rotating shaft seal simply pulls out. There is a thin o ring a few threads in on the bearing carrier, but this rarely leaks.