I would re-seal it using black silicone adhesive, like DC (used to) use. Since you have to change or atleast drain the transmission, now would be a good time to add a PTO filter to the passenger side cover. Last time I had the filter off it had trapped a considerable amount of debris. You probably dont need FastCooler(s) if you dont tow. I have one FastCooler and one PTO filter ($29) on mine. Your leak doesnt look to be bad but if it were my truck it'd bug me.