On my 2006 X drive, The drain bolt is on the opposite side of the fill bolt with the drain bolt being closer to the bottom of the transfer case housing. I believe I needed a 16mm combo wrench as there wasn't enough room for a ratchet/socket. I simply drove the car on a 20 minute roundtrip up to highway speeds, came home, opened and removed both bolts, let it drain, closed up the drain bolt and filled with new fluid until it started to run out of the fill bolt. Pretty straight forward. I don't even think I had to raise the vehicle. And it's only 1L of fluid so you can be done in about 30 mins or less.

On my car, I chose to stick with the BMW fluid as currently, there is no known compatible fluids. The fluid itself looked like a heavy weight motor oil in color and (cold) viscosity.

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2006 X5 3.0L - Schwarz Black/Truffle Brown
Stock
But I keep it clean