North Korea has never used WMD on any other country, and has never used them on their own people. Iraq has used chemical weapons on both the Iranians during Iran-Iraq war, and has used them on the Iraqi Kurds. If I remember correctly from a post here on FR, there was one incident when Iraqs use of a chemical weapon killed many thousands instantly. There were pictures of the dead in the street following the attack.
These facts alone make Iraq a higher priority target.
Not yet, but this problem isn't going away and will very likely get worse in the coming months. Which is, of course, all the more reason to resolve the Iraq situation sooner rather than later, and with extreme prejudice.