You'll definitely need to reseal the entire tank. Unfortunately, new silicone does not adhere well to old silicone, so you'll need to strip all the seals with a razor blade. Then, take a cotton ball moistened with rubbing alcohol to clean up the remainder of the old silicone. When you reseal, the new silicone will need to cure for 48 hrs before adding water to leak test.
This is how I've resealed tanks in the past; however, I have never had a tank separate so I'm pretty much guessing that my method will work. It may not. I hope someone else can come along that will be more helpful. In the meantime, best of luck to you.
