Importing groups of 3D models into Maya can be complicated if you do not know how to ungroup sets of objects. When complex scenes and multiple meshes are packaged in one file they are often lumped into one large object. This is troublesome when you wish to alter different objects in one scene, as you end up selecting the entire scene instead of just one object. In Maya, objects can be ungrouped with a few short commands.
Hover your cursor over your grouped objects. Hold down the "Right Mouse Button" and select "Object Mode" from the pop up menu. Green lines will appear over the meshes, indicating you are now in "Object Mode."
Click on the "Edit" menu and scroll down. Locate the "Ungroup" option and click it. Most of your objects will now have a white outline, while one object will retain a green outline. Your objects are now ungrouped.
Separate your ungrouped objects with the "Move" tool. Select unwanted objects and hit "Delete" on your keyboard to remove them from the scene. If you wish to group objects back together, repeat Step 1 and click on the "Group" option instead of "Ungroup" in the Edit menu.