Rollover effect related to content

hello,

What I’d like to achieve is this:

in the top left content box would be a default for the content. On the right you see a menu rollover thingy. What I would like to do is rollover, say item two which might be home and then in the left hand box it would display an item which explains what the page contains then, if the user rollsover item three which is contact it again provides information on what the page contains on the left.

How difficult would this be to implement, and would I need to load images for the content to be displayed?

Thanks in advance