Thanks for making a DIY compilation post, this will be an excellent resource! Here are a couple more posts I've had saved that may be good to add. Sorry for the formatting, it's the best I could do on my phone!
Engine:
X3 F25 Water Pump & Thermostat DIY (N52) https://x3.xbimmers.com/forums/showthread.php?t=1671793
DIY Spark Plugs for 2011 BMW X3 (35i) chassis F25 https://x3.xbimmers.com/forums/showthread.php?t=1116486
Suspension:
How to: Replacing rear shocks/springs on F25 https://x3.xbimmers.com/forums/showthread.php?t=1731142
Electrical:
DIY: Battery Replacement + Registration + Coding https://x3.xbimmers.com/forums/showthread.php?t=1738900