Making parts of a car disappear depends on the model you use. Some can be disassembled in other apps such as TrueSpace4, some can't. Sometimes the materials in the model isolate such things as the body, and that can be made to disappear within the Render/materials menu in Poser. As a final resort, I have used transparency maps for selected car parts to "cut" a hole or a part away to provide a view of the interior.

Gordon