You can just do a reseal and it should be fine. If you look at the corners of the glass where they are sealed together, if you see the seal broken then you will have to disassemble it completely. Whatever silicone you choose to use, make sure you let it cure for at least 1 week and then do a leak test for another week.
Try to use an aquarium safe sealant. A lot of people use GE Silicone #2 from the hardware store, but it was not designed for aquariums. Even GE does not recommend it as many people have killed their fish and corals with that product.
I highly recommend that you pick up a silicone spreader (versus your finger) from the hardware store. That will give you perfect corners and will make your silicone look like factory issue when you take the masking tape off. Also use a lot of rubbing alcohol as it sticks really bad to your tools and gloves.