I've had both the gears in the roto start fail and the OWB fail. If the shaft of the roto start does not turn then it's probably gears.
Some drills will work, some won't. Try one and see. Just watch for direction of rotation.
Fuel in the tank is not a great idea but for a few days probably won't hurt anything. If it's hot and humid where you're at it the fuel will absorb some moisture as there's no way to completely seal that system. If you want to protect the engine then disconnect the fuel line from the carb, put a few drops of ARO in the carb and spin the engine over a few rounds, you can use a drill for that even if it won't start the engine.