Removing air bubbles...i would get a hard plastic card like a credit card and just try to squeegee the bubble to the edge and let the air out, screen protectors for ipods and cellphones and such come with a little piece of plastic designed for removing air bubbles,
so it seems like the same principle would probably work, otherwise i don't know, those decals are pretty resilient, maybe heating it ever so slightly and smoothing it out would help too.