Eta Carinae is indeed a star in that nebula. The nebula is also often called "The Eta Carinae Nebula" (which so happens to be it's original name), one of a few alternate names to the Carina Nebula officially offered by Wikipedia: http://en.wikipedia.org/wiki/Carina_Nebula. I've always called it Eta Carinae nebula myself, and I know other astrophotographers who also call the whole nebula, NGC 3372, "Eta Carinae" or "Eta Carinae Nebula".
Homonculous Nebula is just the planetary nebula of ejected material from the hypergiant star Eta Carinae itself. That's quite small in comparison to the Carina/Eta Carinae Nebula, which is rather vast. It's one of my favorite regions of the sky...I'm rather bummed I cannot see it from were I live (along with the magellanic clouds.)