Hi Falco and welcome to the forum,
:D
Since you say you have little to no experience with javascript, my standard recommendations for newbies:
1) book for beginners: SAM's Javascript in 24 hours
2) the javascript primer:
http://www.htmlgoodies.earthweb.com
Insofar as your problem:
There are a number of ways to do what you want. One of them is to create a function that executes both actions (rollover link and desc) and to call that function with an onMouseover event handler.
It can look something like this:
<a href='javascript
:void' onMouseover = "swapImages(1)">
<img src="pic1.gif"></a>
function swapImages(imageNum)
{
document.images[imageNum].src = myImages[imageNum];
document.images[ImageNum].src = myDescImages[ImageNum];
}
The above presumes that your image sources are in arrays and that they are set up so that the images for pic1, for instance, are in the same position.
var myImages = new Array();
myImages[0] = 'pic1.gif';
myImages[1] = 'pic2.gif';
var myDescImages = new Array();
myDescImages[0] = 'picDesc1.gif';
myDescImages[1] = 'picDesc2.gif';
You might also want to preload the images so that when the mouseover occurs, it occurs seemingly instaneously.
Hope this hasn't confused you totally :) When you get something up and buggy ( very little ever works the first time except for simple alerts) , post some code or a url and I/we will be glad to help.
Vinny