theres a drain bolt on the bottom, its about 24mm , take this out to drain all the fluid. Then put the bolt back in. Theres another bolt on the side of the gearbox which i think is a 24 too? Take that out and undo the 17mm on the top of the gearbox visible in the engine bay. Then fill the oil up through this hole until fluid drips out the refill level hole on the side. Then put them all back together.