Yes, with that room number, you are definately in a Trans/Dorm unless there is a last minute substitution. And that does happen, I would supposed to be in a Trans/Dorm on the Eagle this summer and they threw in a regular Superliner I that has never seen a refurb at all. It was in surprisingly good condition and still had the window in the upper level bathroom.
As for your other questions, all passenger rooms in the Trans/Dorm are upstairs, except for the handicapped room. The rest of the car contains rooms only for the crew and are off limits to regular passengers. Room 23 is closest to the stairs going down to the lower level, on the opposite side. Room 24 is on the same side as the stairs, providing the staircase wall.
Overall the layout is similar to a regular sleeper, but there is an extra shower on the upper level for you to use. Additionally there is no family room on the lower level and the 4 roomette's downstairs are also missing, that area is basically given over to a crew room.
Of course the other end or crew side of the upper level does not have the normal connector to the next car, but instead a set of stairs that leads to a diaphram that meets single level cars.
