2000 Bravada question about changing transfer case fluid

I was told that to address the "crow hopping" issue on this car to try changing the transfer case fluid. I picked up two liters of "Autotrak

2" at the GM dealers the other day and was getting set to drain the fluid to change it this morning. I noticed on the lower passenger side of the transfer case what looks like about a 3/8 allen size hole which I'm assuming is the drain but I cannot find a fill hole anywhere. Can anyone please telll me where the fill hole is and I guess depending on where it is, if possible how difficult this procedure is on this transfer case? I do have a small "hypodermic" with a short piece of 3/8 plastic hose to shoot it in. Also because I'll have to go out and get one, is the fill plug the same size as the drain and what size is it? Thanks very much. Lenny.