I have 01 X5 3.0, 87000 miles, and I did the transmission oil changed yesterday. guess what, I found there is a big black plug like the one in your pictures at one end of the transmission, I believe it was at the front, and it is not the fill plug. I think 3.0 is different than 4.4. The drain plug is under the pan, front and more on the passenger side as in the DIY article but the fill plug is on the driver side, not on the pan, it is right above the pan, hexagon plug size 17. I and my brother were nervous for awhile because we did not see the fill plug. I will upload the pictures from my phone later to help you see more clearly.

ALX5