Take the swing arm off, last time I had to remove the gearbox, I had it off in 1 hour 35 minutes, that's from walking up to the bike, to placing the removed gearbox on the workbench .
It may seem like a lot of work, but it really isn't, after you get by any issues with rusty/seized fasteners or previous foul ups from previous owners/mechanics, and the like .
Make sure you get the 4 bolts that hold the drive shaft to the gearbox output flange loose first, as after the rear wheel is removed and you can't use the brake to hold things still, it can be a real job to get those loose .