The "shell" of the new MacBook might be more than you think it is. In these notebooks, it is the main structural support, and also the foundation around which the other components of the computer are secured to. In order to replace this, virtually all the other components of the computer would have to be removed, then re-installed on another "unibody," the term Apple has coined for this lump of aluminum. In other words, it might end up being cheaper to just replace the whole computer, rather than just that part. Templeton Peck said the only way to find out is to call , and I agree. That would be the best way to find out. Also, don't forget to mention that you are in the military (or something to that extent). They may be a little more sympathetic and willing due to the more hostile environment one might find at such an installation. If Apple does go as far as replacing the computer or one of the components, they will take care of shipping and handling, so you won't be making 800 mile round-trips either.
Best wishes,
Nathan