As elmarcorulz said, you'll need DVD Shrink to compress a DVD-9 into a DVD-5. It does not come with nero, although you can use nero to burn the converted files from DVD Shrink to a DVD.
It's a free program, so there's no harm in trying it.
As for the difference between Premium and Ultra, I read somewhere that they are exactly the same thing. It's just sold as Ultra for USA and Premium for the rest of the world.