If the shaft has come loose, it may be the result of other problems (like a slight warp in the shaft). Most distributors don't use a bearing at the shaft -they ride in journals.
Which way is the "play" in the rotor? Can you move it side-to-side? In/out? Describe the looseness.
As for internal and external coil... If you have five spark plug wires (four going to plugs and the center one going to a module bolted to the back of the head), then you have an EXTERNAL coil.
If all you have is four wires, each leading to spark plugs, then you have an INTERNAL coil.
If you do have to replace the coil, have you checked Ebay? I know that shipping to Australia is going to be high, but maybe you can find one pretty cheap so that it's not too bad.