Fixing a gap with silicone on shower base
You have a good plan. Make sure the area is totally dry before applying the new sealer. Scrape the area with a single edge razor blade to remove all the old sealer and then wipe the area with some vinegar to remove any residue. Stuff some paper towel in the gap to make sure it's totally dry, then apply some quality silicone caulk to the gap. Check the rest of the tub for any other failed areas.