Is it possible that I will see some of the questions that I have been practicing on the GMAT? Or is there an entirely new (and different) pool of questions used specifically for the actual GMAT?

I doubt that you'll see questions that are EXACTLY the same as ones that you've studied. However, you definitely could see questions that are very, very similar (think: simply changing the names or numbers slightly). I've certainly had some actual GMAT problems that were strikingly similar to problems from the Official Guides - though I don't think word-for-word.

So, my general advice is don't bother memorizing problems - instead, understand the underlying concepts so that you can do similar, but slightly altered, problems.