You have to read all the word signs that are in the hallways because it will lead to a puzzle at Bauer's door that you need to have all the letters to solve. You can read them at a distance - I got as far away as I could so the monks didn't see me.
When you see a monk coming down the hallway, step close to one of the many doorways. They won't see you there. After he's passed, you can even follow him a little.
Imagine the area as a square hallway with a path down the center (which you don't need, really). When you first get in, the office is in the hallway to your right. The storage room is where you need to go first because you need something there that's on the floor so that you can get into the office.