How much volume of power steering fluid do we have in the E39?

Is there a picture somewhere that can tell me which hose to pull?

Is there a specific sequence to follow, in terms of when the hose is pulled vs. when the car is running?

This sounds like a 3 person job?
One guy watching/diverting the hose, one guy turning the steering, and another guy refilling the reservoir?

Making more of this than warranted. Loosen any connector at the pump so gravity will drain pump too. Re-connect. Go back up top and fill reservoir. It will release big bubbles as some air escapes. Re-add P/S fluid as necessary to keep full. Start car with fluid handy. see if reservoir needs more. Turn wheel lock to lock and you will hear P/S pump quiet down and take a little more fluid. turn left to right a dozen times and top off. Drive ten miles or so and then do whole thing over again. Couple times will replace darn near all of it. One man job!

Things are always easy and obvious in hindsight. Not if you've never done it.
Heck, I don't even know where the PS pump even is (yet)

Do you disconnect the PS pump and then start the motor?
Or is it just disconnected to drain the pump and then reconnected?
Is it dangerous to drain the PS pump and have it empty until the new fluid reaches it?
Should you wait to turn the steering wheel for a minute or two, so the new fluid has reached the PS pump?
When the PS pump hose is disconnected, do I run the car and turn the wheel?

Empty and fill with engine OFF. Don't run with pump dry! Fill slowly and it will get to pump w/o engine running. You can turn key to pos.2 and rotate steering wheel w/o power assist, but if you just fill over about 5 minutes, most air will be gone. Then start and quickly turn wheel lock to lock repeatedly.