Hi, Kelly. I kind of agree with lawnboy. I would wash it with Tri-Sodium Phosphate (TSP) and rinse well but using as little water as possible. Use a sponge and just keep changing it often, otherwise your downstairs neighbors might have something to say. It would not hurt to hand sand any areas where the old finish is still shiny, then wipe those with a damp sponge to get any dust. Usually, I suggest oil based poly but I think that you will be better served with water based poly. Oil based takes a good 24 hours before you can walk on it in stocking feet. Water based dries much faster. Oil based is a little prettier and more durable, but the water based is not far behind. Don't paint yourself into a corner.