Well, I'm not familiar with elements, but once you click on the magic eraser, you can set the tolerance (I think that's what it's called) this will determine how much the eraser erases (for instance, it will erase more or less of a certain shade). Just mess around with it, you should get the hang of it. You might have to use the normal eraser too, because I never find that the magic eraser works the greatest. Once you get everything cleared, save it as A PHOTOSHOP DOCUMENT (this way, you don't lose all your hard work). Then go and re-save it as a different name and edit the background how you like by adding a new layer and putting it behind the photo (Idk if elements has layers, if not you're out of luck and should try GIMP).