I would suggest making two bases around 3'L x 3'W x 3.5'T, these would be small enough to carry down the stairs (if your hallways are wider than 3'
) Then I would mount a one piece top 3' x 10' that you can fit through the window (shouldn't be a problem since you need to get the tank bottom in the same way) The one piece top should be rigid and dead flat to ensure there are no stresses on the tank. My thought's anyway...
Francis