You can upgrade to a higher level for the difference in the cost between the one you have and the one you want. Sometimes that is the easier way to get up to the Deluxe Pass. It depends on how close you are to renewal time. If it's still months away, then figure out how much your current pass cost and how much the deluxe pass costs and the difference between the two will be what you pay to upgrade. You can do it at the AP Processing Center on Main Street.
Why not wait until Sunday? If the only day you can go is Saturday then yeah, upgrade. If you can wait until Sunday or next week to go, then I would do that. I don't recommend buying a blockout day pass. It seems like a big waste of money to me.