I agree, since it is already empty I would re-seal it now. Better now while empty versus after the tank is set up, has live rock, fish, and coral that would need to be broken down if a leak developed later. There are plenty of videos on line and many in the club have done this and have experience. I recently resealed a 220G that I was setting up. Probably didn't need it, but it was better to take care of it while it was empty just to be sure. It is a lot of work and you do need to pay attention to the details so that you have a good water tight seal afterwards.