So I need to swap out the brake reservoir. Looks like its held in place by just these two slots in the master cylinder, with o-rings maybe? Should I just pull it up till it releases or is there some kind of special way to remove it?

 

Its just pressed in there, you're gonna have to do a complete brake bleed procedure.
Start with the right front, left front, right rear, then left rear. Follow the same order until all the air is out of the system.

 

i was always taught to work starting with the furthest wheel right rear, left rear, right front, left front

 

Not on these cars, the factory repair manual says just about for all audis in that sequence.
That sequence works for almost all other cars.

 

^^^Really! I always thought it was the other sequence. Yea I'm doing the brakes at the same time so it'll have to be bled anyway. So its just stuck in the master cylinder right, no o-rings to replace also?