If it is just a stress crack let it be. If it is mo big and lettting water in, rout it out just 1/8th wide and very shallow (don't cut through the hull), then fill it with thickend epoxy (West Systems would be best but doubt you have that if a newbie) Use a high quality 30 minute epoxy if no WS epoxy. Use masking tape to build up a barrier alla round the edge of the area to be repaired, carefully fill the routed area with the epoxy with a tooth pick, slowly to avoid build up and run out. Prop the boat up with old batteries so the area to be repaired is level with mothe rearth on the x and y axis (front to rear, side to side). Let it dry for a minimum of 12 hrs, 24 is better. You can make this same repair with white gel coat repair that comes ina kit, it is sold by your local boat sales dealer but it is expensive.
