> Where can I buy sheet metal??
At the hardware store, yes, ask for aluminium flashing. It's used for gutters. ^__^
> second, if somehow i managed to get my hands on some sheet metal, how do you work with it? what tools are needed to bend/shape/cut/etc it?
I've been told that you can cut it with an exacto knife, but being a weak girl I got metal snips.
If you want crisp folds, you should also get a special tool for this.
Ad for the edges, you will need a metal file to make sure you don't cut yourself (or anyone else). Said metal file can also be used to roughen up the surface of the metal if you are planning on painting it, making it easier for the paint to adhere.