YAY!
Yeah, you could sand it down and re-stain it. You could also put a plywood sheet on the bottom of the tank as well, and then chalk it and they epoxy paint the inside completely so that it would be easy to clean from mold and mildew. Also if there is any overspill from your sump the bottom of the stand can hold a few gallons of water so that it's not all over the floor or better yet - carpet.
I would recommend epoxy painting the inside of the stand, at least so that it would stay clean and that humidity won't degrade the wood over time. I wish I did it on a few tanks that I built. lol. Good thing now is that you have the opportunity to do so!