I'm working on the same problem myself. Right now I can comment out a few lines of code and get the car to import but be invisible (You can only see the ghost)
I'm pretty sure it has something to do with the shaders. I'm sitting down this weekend and next to see if I can re write the shaders and model importer so that I can bring in any .x or .fbx model.
Let me know if you figure anything out and I'll do the same.