Will I need to re-sand wood that has raised grain due to moisture?
Sanding oily wood will quickly ruin your sand paper. However, whether it should be resanded depends on how much you care about the finish. 
As a matter of practice, when I make "fine" wooden pieces, I purposely wet the wood after my first 220 sanding; after allowing it to dry, I sand off the fibers (or grain as you mentioned). And I sometimes repeat the wet, dry, and sand routine if I really need get rid of those fibers. I do this so that few fibers appear if the wood accidentally gets wet, or especially if I am planning to use a water based polyurethane to seal it.