Currence from the future. I like it.
With a modern photo-editiing program and printer it should not be too hard. The hard part, as usual, is paper. If you want to do it right, get some new one dollar bills, bleach them, or at least the part that you intend to alter. Then put a picture of George Bush, Hillary Clinton, or even somebody far out, like Farrakan, to replace old GW. If you do it right, it would be convincing.