[Fyron]

You can certainly upload a replacement turn for the first turn. It does not have to use the same empire files, or the ones that are stored on PBW at all, really. Go into the game admin screen, and scroll down until you see the Upload Replacement Turn section. Enter the location of the replacement turn to upload (zipping makes it smaller), and click on the checkbox there that will make it replace the current turn, rather than upload the next turn manually.