Separating parts of a 3D object for isolated functions in Unity I am curious how I would accomplish the following:

I have created a level with walls, ceiling and flooring (all as one solid 3D object).
I then want to be able to import the object into Unity and once in Unity, I want to be able to select only the walls and give them a tag "wall" as well as be able to drop a texture onto the walls using unity and only have it texturize the walls, not the entire game object.  Same for flooring and ceiling.
Unity imports work just like the Blender inspector shows. If you have a Blender scene named Shapes and it has a cube and sphere, when you take it into Unity you will see a empty named Shapes that has children called cube and sphere. The whole scene can be moved by selecting the Shapes empty or you can do it individually with the children. You can do whatever you want (components, materials, textures) on an individual child or scene wide level. If an object is parented, lets say cone is parented to cube, it will show up as a child in Unity.