Help needed...making a mould

Ok guys here's my problem..
I have a stormtrooper bucket that is a very good replica except from one thing, the face from a front view seems to be slightly to wide.
How do I go about making a cast/mould of this bucket without damaging it. I would prefer to make a cast/mould then work on that rather than attempting a repair job as I have no knowledge of casting/moulding.
Any help at all would be greatly appreciated.

Sounds a bit like like recasting. In all due respect, if you don't have the technical knowledge to do a mold.... than I doubt very much that you could sculpt a better storm trooper.

yup, if its an expensive helmet, I wouldn't touch it with inexperienced hands. With any project, you expect your piece to be damaged but the key is to minimize it as much as possible. This process I can't even begin to explain without having to show somebody in person let alone write about it. Seriously, leave well enough a lone, besides, the stormtrooper is not supposed to be symmetric...the asymmetry the better.

Thanks guys, I feel a little deflated but better that than destroy my helmet.
Thanks again.