You do get free parking but also get free parking any time you're staying on property. But if getting the free parking is worth the extra expense, I doubt it's worth it to upgrade during your time. I would expect you'd have to pay the full difference for only part of the year. Of course you could just do this for one pass if parking was the only issue. Remember the savings over the FL residence AP is not $100 but only $20 or $25 (I forget which right now), and I don't think it'll save you anything on the renewal price.