Whenever I load a tank with textures shown, it explodes into a rendering mess of spikes and edges that fly around the place.

Oh my.. That isn't good. What video card?

As far as the FBX.. You can get a converter to update the FBX so apps that need a new version can read it.
https://www.autodesk.com/developer-network/platform-technologies/fbx-converter-archives

Closing this.. Respond on other issue thread.