I'd fill it up, dry the outside with a dry towel and see where the water is coming from. If its a small stream or drips, I'd just smear some new silicone on top of the old and call it a day.
I would not reseal the whole thing. Worst case I'd cut as much silicone as I could from the 1 leaky area and reseal that whole side.
Resealing an entire 100g tank is going to be difficult, time consuming and fairly expensive. Don't make extra work for yourself unless you just like the work.