Not true. I have your vehicle , 01 with 241,K miles on it, original tranny. I changed the filter and pan full fluid every 60K. Bought the X with 32K miles on it. Two things to be aware of: 1. Be careful not to strip the fill plug. 2. Don't over-tighten the drain plug.
As for the torque converter amount, you can let the tranny drain overnight, a small amount will continue to flow. But don't worry about mix unless you have excessive miles without tranny fluid change. BTW, how many miles since last change? Be sure you have the proper fluid for change and then stick with it. BTW, yesterday I had my first (gearwheel) transafe come on, but it went away when I started it back up. Good luck.
You can pay for the complete flush at dealer and then do them yourself to save money.

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X5 3.0 AUTO -2001 - 238,000 miles