Its not so bad, quite a few of us have blown up gearboxes.
Its an easy job taking out the box if you are organised and have a place to work. The most important advise is to take loads of photos as you take it apart.
You will also need to construct a fixture to cradle the engine, the bike is dead weight when the rear end is dropped off.
Last time i took out a gearbox it took me less than an hour.
Dont hesitate to PM me if you need advise.