Stop leak will not fix a leak at the shaft seal. I would think the dealer would replace the pump for free. For the electrical problem check the simple thing first. Is the light switch off? If so remove the cover from the cutout relay and check the points, they should be open with the engine not running and the small wire disconnected at the starter. If they are welded closed you need a relay, if thay are open but close when you touch the wire to the starter you have something hooked up wrong at the generator or in the box. Check down the posts here for a guy named Duey, he has a nice site with correct wiring diagrams and he posts the link most of the time. Also make sure you are wired for a magneto and not battery ignition. The wire from the magneto is simply a ground though the switch.