The easiest way to tell if you have second printing is to look just inside the cover - if the sheets are black, you have second printing. If the sheets are white (or if you have 3 logos on the back), you have first printing.
If your store still has a copy of First Printing on their shelves, we are offering them to replace the old copy with a second printing (they will need to donate, destroy or otherwise not sell that first printing copy). They can drop an email to firstname.lastname@example.org
for more details.