Originally Posted by FlyerChrisK

It sounds like you've already ticketed. Changing from G to W now would almost certainly require a change fee and repricing the ticket as if you bought it today. If you haven't ticketed, consider routing through California as that's eligible for UDU/EUA.

Op-ups are always possible, but I would not count on receiving one. Out of my 86 regularly scheduled, commercial flights this year (60 of which were on UA/CO), I received a total of three op-ups: Y->J for a VDB, Y->J for an op-up, and J->F for an op-up, all on United's p.s. service.