Oooh goody. I love a good gearbox oil issue thread.
Fill and drain plugs are on RH side of gearbox (

).
The drain plug is just above the header (near the rear brake lever toe bit) and needs a 14mm hex drive. Room is very tight so a 1 inch piece of Allen key and a 14mm spanner are your best bet.
To drain the oil out I use a old milk bottle container with a piece cut out if to form a funnel (0.5 ltr or 1 ltr works best) which keeps the oil from draining on to the exhaust.
If you work it out you can then use the same cut down milk carton (modified) as the funnel to put the new oil in ( a sort of horizontal funnel). Don't know the size of the filler plug ( side of the gearbox) but it is a standard hew drive.
Before you ask, no, there is not a crush washer on the drain plug bolt. Just sack it up tight (using the recommended torque setting of course

)
DT
Ride like your life depended on it.
2002 BCR