Ok Sparkly Giblets. (love the name by the way) Here's a brief description that should set you on your way.
First of all. Clay which you say you have. You can sculpt the clay on a head blank, the styrofoam ones that they display wigs on, this will give you a good size referance as you don't want to look like a bobble head when wearing your bio. Or you can use an open face crash helmet if you have one lying around.
So you've slapped the clay on and you are happy with your design and finish. Now it's time to make a mold. Get yourself down to the hardware shop and grab some tubes of silicone, Using latex gloves smear a thin layer of silicone over your clay sculpt making sure to get rid of all air bubbles and get into all those little corners. Once this is done leave to cure, you can speed up the process by using a spray bottle of water and misting the silicone. Once dry apply more silicone. this can be up to 5mm thick, no more as it'll take ages to cure, once again the misting method can be used to speed up the process. Repeat this stage till you have about 20mm of silicone covering all of your sculpt.
Next you need a plaster jacket. Most people use UltraCal, but you can use dental plaster or even plaster of paris but you will need to reinforce this with burlap or plaster bandage. Mix up the plaster and blather it all over your silicone till you have a thick shell at least 20mm thick probably more. Once fully set (and this will depend on conditions), you can start to remove the clay.
Once this is done you should have a nice clean silicone negative of your Bio. If you have any bits of clay left in your mold clean out with a bit of water and a soft cloth then dry it off. Next dust with some baby powder (lightly) this acts as a release agent for the next step.
Resin. This is down to personal taste. Some use fibreglass resin and matting, some casting resin and others a mixture of both. Lay up your resin/matting in stages till you are happy with the thickness and then comes the exciting part, taking it out of the mold. If all goes well you should have a bio that looks great and a mold that's in one piece and that you can use again to make more copies.
Hope this helps you out. And don't forget to post pics