The engine does not need to be removed.

Disclaimer :
I would not recommend anyone attempt this, unless they are competent in their abilities.

According to the Service Manual, the Transmission is of a Cassette type design,
which allows removal of the complete Transmission as an assembly with the front bevel box.
Transmission Removal :
1. Disconnect the Battery
2. Remove the left side Upper and Lower Fairings
3. Remove the Gear Linkage cover
4. Remove the Clutch
5. Remove the Rear Bevel Box
6. Remove and discard the 10 Transmission fixings ( bolts )
7. Withdraw the Transmission assembly from the two Crankcase halves, collecting the two location dowels
After removing the Transmission, the instructions in the Service Manual
should be followed to remove the Selector Shaft, Drum and Forks etc.
Cheers

