Shane,
Did a little work on the model for ya. I started from scratch and built a closed mesh for you. I used your mesh to indicate the general shape, but replaced every polygon except those in the door handles and bucket seats. I don't claim that it is perfect, better, or that I am some guru expert, but it is much smaller, and with the 2 exceptions above, is a closed mesh.
Open it up, click on Tools -> Mesh Tester. It will highlight the areas in the mesh that are not closed.
Anyway, gave it a real quick skin and zipped it for you to play with, finish, or delete. Might be too low poly for ya. Maybe you want to do another one that is more detailed, but closed?
Charger2.zip Cheers!
Mark