PS - Funny guys take note - I am not a complete moron. I have read the owner's manual and it does not contain the required information. Hence I am putting myself at your mercy....... Duh!!!!

generally, open the plug up, stick your pinky in the hole, and the fluid should be just under the oil plug. they have little inserts for the gearbox oil oil jugs. just stick it in there and fill her up.

check with bmw agent but think these units are 'sealed for life' and have no level guide