General - Editing a different face onto a poster?

This may be way out of line - forgive me if it is - but I'm looking for professional help! I'd like to edit the faces of a couple of friends of mine into a Mr. and Mrs. Smith Poster, along with their last name, of course. Is that legal, doable, and who could make it look like the real thing - not a photoshop noobie job?

Thanks!

I could probably give it a try.