Great point, MyerPJ - just Google free green screen footage and download a few clips to play with to get used to keying in Premiere.
But keep in the mind the download clips will usually be VERY easy keys and not what you will experience the first time you try it, so again test test test with your own footage and leave nothing to chance - the Bank President will not be pleased if he/she has to come back for a re-shoot.
Thanks
Jeff