Drain plugs for the transmission are near the bottom of the output shaft housings, facing towards each other just as the housings start to go vertical (the plugs are horizontal if I remember correctly.) I think they are a 3/8" NPT plug, maybe 1/2". The drain plugs are in a similar location on each of the front final drive housings. I don't think the fronts have a plug for how far you're supposed to fill it to. You just add a fixed amount of oil which I'd have to look up the amount for. Maybe a couple hundred milliliters. The main transmission has the dipstick of course.