You may have difficulty finding space in First on the earlier SFO-OGG.

Definitely try to do SDC, though. Re-checkin with the United App. If Earlier flights are available, you'll see a graphic that says switch to an earlier flight during checkin (it looks like an ad, so don't ignore it).

You can do it after UA sees that your LH segment has been used, so technically as early as on the plane en route to SFO if you have Internet.

If there are no options, keep trying in case space opens up. You can try again at SFO or at a kiosk, or with an agent.