Re: Brake-in period.
Not long. I assume they 'bedded' the pads for you after they changed 'em? (If required, they most likely did).
Basically, they want you to drive slow so that you aren't needing to do any emergency stopping. Brand new brake components need a bit of "wear and tear" before you can start brutalizing 'em.
Just don't do any hard braking for the next hundred miles or so, and you'll be fine.