Answer:
This task is a hard one and could only be done by professionals like m- eem.. professionals.
But you should try and figure out all the staffs daily routine. Then you could take the staff with a key down sometimes when he's alone. I would recommend using parafyl- i mean some liquid that i dont know about.
Then you try and bypass the alarms or trigger them and just run away. Always hide your face and fingerprints. Lay out your escape ruit before you run.
I mean THEORETICAL of course (wink wink ;D )