The oil change is easy at this point, nothing to really say here. The transmission service, while not specifically easy, is time-consuming and requires you to run the car and then top it up. It seems like the BMW-authorized procedure has been bastardized by the numerous YouTubers that have done this before, so I cannot provide a 100% accurate method for making this happen. What we did was drain the old fluid, remove the pan, replace the pan, fill it up until it's running out, run the car on the lift until the transmission is up to temperature, and then re-fill. No kidding, and not just the placebo effect, the car shifts way more smoothly than it did before.
There was no metal within the pan, and the fluid, while a bit stinky, wasn't even really that dark.
We also took the time to decontaminate the underside of the motor. What a mess these things make of themselves when the valve cover leaks over time (our first repair to the top of the motor, but this is the first underneath cleanup). This will allow us to watch for new leaks, etc...
Here's to another 137k.