You can choose to get to the guest quarters one of 2 ways:
If you go in the front door, proceed to the chapel area at the back of the main piano room and head down the stairs. At the bottom of the stairs is a room with several linked Epic x2 mobs, assorted Heroic ^^^s and occasionally the Count of Somnborn. The guest quarters are off the side of this room down another staircase and right, down the hall.
You can also approach the guest quarters from the bottom coming up through the catacombs. Take the hall south from the spiral staircase, proceed up and then West at the T intersection straight past the Maid's room and the Fountain room will be the guest quarters.