They're just stickers, mine are anyway. I had a decal on an old car made of the same stuff. It looked awful, so you can warm the glue up with a heat gun and pull them off.
I'm sure fleabay will be able to provide you with a new set, but if your old ones are (well) old, it's fairly likely they will have faded, so you might as well zip off the lot and start again.
(by the way, I read your head gasket woes with interest and I hope all is good with that now)