MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
The staircases should print in the M3D if they are rotated around the z-axis. No resizing should be needed.
(I may be mistaken, though. I no longer have an M3D...
If it does not fit, I'd slice them in half horizontally, and glue them up afterwards. Meshmixer does a pretty clean job of splitting.