The item you would need is a Lens spanner. This is a device that is a bit like an old set of compass dividers, except that it has screwdriver like blades at the end rather than sharp points. These open up and then the blades slot into the little grooves that you see around the front element of the lens. Think of it a bit like a tool to remove watch backs.
However as Nexus has said - you could end up doing more damage - if you slip there is a chance of the metal scratching the surface of the glass element.
The lens is an L series lens? Well worth getting it fixed professionally.
The other problem you may run into, is that when you put the front element back in place it might not be optically centred (collimated) and as a result may not focus accurately.
Canon do offer a repair service and there are others, such as Fixation, H. Lehmann Limited and I'm fairly certain other people will recommend some additional repair centres.
