Your right, there is a major construction project at Slussen (been going on for a long time). Was a bit afraid of that but we didn't hear anything. It was very quiet because there is no car traffic nearby. Staying there again this week, so I'll update TripAdvisor if anything has changed.
Information about the room from the hotels website:
Suite. Bedroom with a King size Haesten Sheraton Bed. Living room with sofa, arm chairs, table with chairs, tile stove and TV. Desk with telephone. Wooden floors Wireless Internet connection. Bathroom with shower. Hairdryer. City/lake/river view
-> so the room has private bathroom and shower.
It's only the Economy twin room that has shower and WC in the hallway
You can take the red or green metro line south two stops to the Slussen stop - the hotel is around the corner. Keep in mind that you have to walk all the way around the hotel building to get into the entrance.