Help A Newbie Out With Upgrading Using Points

Wife and I are traveling to Japan as part of a group in Feb-Mar '27. The group purchased cheap tickets on United, and we're unable to upgrade those seats. We're trying to buy and upgrade to a more comfort or ComfortPlus with the ~300 Capital One points. The group will reimburse us $1800 for our 2 tickets if we go on our own.

We're able to do a positioning flight from NC, especially since my wife needs to return to Chicago for work the day after we return. Depending on what airline we fly, we might be able to move Delta SkyMiles over to assist in getting more points.

I'm nervous about doing this myself and screwing it up. Are there services that others have used to make this happen, or anyone willing to help?