Need help with displaying and hiding images

Ok, I have a product gallery that I am using here.

www.oxbowcreations.com/slaters/jigs/test.php

I want it to do this:

www.oxbowcreations.com/slaters/jigs/cajun.php

The only difference is that I want the image to stay visible when you click on the style drop down on the right. That's why I can't use the CSS. So I try to do it with javascript and the first link is what I get.

As you can tell I don't know much about javascript and any help will be greatly appreciated.

Here are the functions
PS how do I use a mouseover without using the onmouseover="rollOut(itemNum)"?

Code:

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<script type="text/javascript">
/*These are the thumbnail rollover controllers*/
var flag = 0;

function rollOver(preview) {
        if(preview.flag == 0) {
                document.getElementById(preview).style.display = 'block';
        }
}
function rollOut(previewOut) {
        if(previewOut.flag == 0) {
                document.getElementById(previewOut).style.display = 'none';
        }
}
function stick(prevID, itemNum) {
        var prevPic = document.getElementById(prevID);
        var sku = document.getElementById(itemNum);
        prevPic.flag = 1;
               
        if (prevPic.flag == 1) {
                prevPic.style.display = 'block';
      //This is the command to display the item number
                sku.style.display = 'block';
        }
}
</script>

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If you need any more code let me know.