FBJS image slider - fbjs

Question

Im trying to recreate a slider similar to:
http://www.facebook.com/BacardiLimon?v=app_146177448730789
but apparently there is zero documentation on how to do something like this with FBJS :'(
var eCardPos = 0;
var totalCards = 4;
var animationFadeTime = 300;
var cardUrls = [];
cardUrls[0]= '';
cardUrls[1]= '';
cardUrls[2]= '';
cardUrls[3]= '';
function changeEcardPrev()
{
eCardPos--;
if (eCardPos < 0) {
eCardPos = totalCards-1;
}
showEcard();
}
function changeEcardNext()
{
eCardPos++;
if (eCardPos > totalCards-1) {
eCardPos = 0;
}
showEcard();
}
function changeEcard(pos)
{
eCardPos = pos;
showEcard();
}
function showEcard()
{
var elCard = document.getElementById('cardImage');
var elLink = document.getElementById('cardLink');
var elPreload = document.getElementById('preload_card_'+eCardPos);
for (var i=0;i<totalCards;i++)
{
document.getElementById('cardButton_'+i).removeClassName('active');
}
document.getElementById('cardButton_'+eCardPos).addClassName('active');
elLink.setHref(cardUrls[eCardPos]);
Animation(elCard).to("opacity", 0).duration(animationFadeTime).checkpoint(1, function() {
elCard.setSrc(elPreload.getSrc());
}).to("opacity", 1).duration(animationFadeTime).go();
//Animation(elCard).to("opacity", 1).duration(animationFadeTime).go();
}
I happened to find the src but I dont even know where to start :\
EDIT:
I think I found something that might help but the images slide :\ I just want them to appear when a direction is pressed.
var numslides = 3;
var slidesvisible = 1;
var currentslide = 0;
var slidewidth = 300;
function goright() {
if (currentslide <= (numslides-slidesvisible-1)) {
Animation(document.getElementById('slideshow_inner')).by('right', slidewidth+'px').by('left', '-'+slidewidth+'px').go();
if (currentslide == (numslides-slidesvisible-1)) {
Animation(document.getElementById('right_button')).to('opacity', '0.3').go();
Animation(document.getElementById('left_button')).to('opacity', '1').go();
}
if (currentslide < (numslides-slidesvisible-1)) { Animation(document.getElementById('left_button')).to('opacity', '1').go(); }
currentslide++;
}
}
function goleft() {
if (currentslide > 0) {
Animation(document.getElementById('slideshow_inner')).by('left', slidewidth+'px').by('right', '-'+slidewidth+'px').go();
if (currentslide == 1) {
Animation(document.getElementById('left_button')).to('opacity', '0.3').go();
Animation(document.getElementById('right_button')).to('opacity', '1').go();
}
if (currentslide > 1) { Animation(document.getElementById('right_button')).to('opacity', '1').go(); }
currentslide--;
}
}
How would I get the image to fade in and out rather than slide?