Everything that has been said is true (and I also didn't realize how many MDs/keyboardists there were on this board!), but I'll also add that Spelling Bee is a MONSTER of a keyboard book, in terms of programming. If you're not familiar with Mainstage or Forte, it could take you DAYS of programming, possibly even weeks. And yes, you'll definitely need a patch change pedal, so make sure the keyboard you're using has enough input jacks for that.
Without knowing more specifics it's hard to give you advice (what rig you'll be playing on, what the budget/professional level of this production is, etc.), but the bottom line is that this will be a tough show for you to dive into keyboard programming on. I recommend seeing if the theatre will spring for the Keyboard Patch Solutions that trentsketch mentioned. Then after this show closes you can learn Mainstage or Forte on your own time and be ready for the next one!