Mouse over text changes a target image

I’m sure this is a very simple thing, but I just can’t get my head around it.

The link that I’ve supplied actually points to an old site that I built about 10 years ago using Adobe GoLive, before I discovered WordPress. You will see the effect I’m trying to achieve – when the mouse hovers over the text, the image changes slightly.

I still have all the images and access to the old html files, but I can’t work out how to implement this effect in my new WordPress site.

I have tried playing around with an old plugin called IMG Mouseover, which sounded like it could do what I wanted. But it seems to be broken with the more recent versions of WordPress.

Any help would be thankfully received.

The page I need help with: [log in to see the link]