Otherwise there will be a lot of back and forth trying to decide what needs to be included and what can be removed. if this isn't going to be a 'take apart' showing interiors (like a high-end dollhouse) then find a way to scrub the internals from the exterior. Make sure it's clean and simplified first e.g. You'll need to provide a file, typically an STL but most will accept other neutral formats like IGES. They'll handle all of the fine details like splitting it up, picking appropriate materials, adding printing supports, and so on.
To get a good 3D print, I would advise finding a company to do it for you if this is anything other than your main job. 'Overheads/overhangs' are easy enough to handle, not everything needs to be printed in the finished orientation, and most printing software can add supporting structures. 3D prints can look great in industry shows and lobbies.
