mnoe: welcome!
there are two types of exchanges. Future exchanges and unused ticket exchanges. If you realize you can't / dont want to attend a game at least 3 days in advance of the game, you can pick a non-blackout game and get similar quality seats to what you are giving up, depending on availability. The new seats will not be an upgrade. If you already have seats to the game you pick, then you will have a second set of seats of similar quality.
I don't know if there is a way to pay the difference to upgrade, and I don't think you can stack your old seats with your turn in seats and upgrade that way, either. If you can pay the difference when you upgrade, you could try to stub hub your current set, which is allowed, and recoup the difference that way.