[gb2world]

Anyone knows how to modify the language like "Previous" and "Close" in the shadowbox.js file when using the Telafirma mod? Sorry for asking, I am just a total javascript n00b here... I searched on the http://mjijackson.com/shadowbox/ site and forum as well and there's an option to change the language but that shadowbox.js looks totally different than mine...

The file you see on the shadow box website is likely very close to the same thing in terms of code that you have - but the one in the TelaFirma distribution is compressed (linebreaks and unneeded space and comments are removed) - so it is a little harder to read and edit. But - you can see the same code if you search for it - and change the text to be what you want:
search for:

'<span class="shortcut">N</span>ext'

change to

'<span class="shortcut">S</span>iguiente'

etc.
The span class is creting the linked item in the popup - so you should be able to set that as you wish as well.