I'm so green at js...

I need a onMouseover script that will allow the following action: when one image is rolled over, another image (although a div would be much better than another image) would fade in. I really like this script from dynamic drive, but it only allows for text to appear, where I need a div or image...but at least that's the general effect I'm looking for.

I'm fairly knowledgable in html and css, so if someone could point me in the right direction for a script (or if there's a way to customize the above script to allow it to include a div), I should be able to figure out the implementation. Gah, sorry for being so vague! Please feel free to ask questions and maybe I can help clarify if necessary. :)