That is good news that it does come out , i had a similar plug on a kawasaki enging side cover, i ended up making a tool to undo it out of a piece of flat stainless metal kind of like a giant screwdriver tip then clamping it in a pair of mole grips and with lots of force pushing against it while turning i eventually got it undone, you could try heating it up before attempting to undo, and if it is the oil gallery plug and its leaking the chances are the threads are well oiled so you stand a good chance of undoing,
pete