Some help, please...

I'm currently working on a website, and I've hit a deadend. I have a text link on the right side of the page and an image (image #1) on the left side. When you roll the mouse over the text link, image #1 changes into image #2. Is there any way that I could get image #2 to stay there after clicking on the link? And if there is, how do I structure my code so that rolling over other text links will bring up, for example, image #3 but switch back to image #2 when I move the mouse away?

My site is here if you need to see it, just right-click View Source (I'm not sure what part to post, and there's a lot of code there, otherwise I'd just post the excerpt).

Any help or ideas are greatly appreciated.
~Sarah