if he can buy the ship without crashing then odds are the mesh is fine and it is just a problem with the textures. One myth i hear a lot of which is incorrect is "if your textures aren't flipped they won't appear". No, think about it, it only changes how the picture looks, nothing else, who is to say which side is up or down? You could easily just texture it upside down on purpose, not flip the textures, and it would look perfectly correct in game. (note all references to flipping is also only if you use the .tga format instead of .dds) What will happen if you use a targa and not flip it, it merely takes what would be mapped as the bottom of the texture as the top, your ship will appear, it just won't have the same mapping or look the same as it did in milkshape. Moral- if your textures don't appear on a ship, it's not cause of flipping or not flipping textures.
what can cause textures not to appear:
not using a valid format -uncompressed targa or direct draw files
a typo of the filepath for the .mat in the shipsarch
a typo in referencing your materials name in the .mat which the ship mesh looks for, however with the advent of the .mat exporter this error has virtually been eliminated.