Originally Posted by JJeffrey

There is indeed only one seat left in business on your flight (J1C0) so it will be tight. The earlier flight is wide open though as you said (J7C7).

There's no same day change options on international flights like domestic. So to change you'd pay the change fee plus/minus the fare difference, if any. And SWU request date follows the flight, so that would start over...although that's irrelevant as you could confirm the upgrade immediately.