Wanna add a "latest image from gallery block to the left side of site!

Okey what shell i do here I have understood so far that i will have to do something like this.

Here is website: http://stureplan.mine.nu (wow guild site)

1. Change main.tpl and add a block to the left side.

2. In that block add somewhat of code that tells another script in like header.php or something to fetch something in functions.php (in functions.php i place the php code that is necesarry).

3. How do I do this not so good at programming php but i still get the buildup of it ^^^