The oil could be leaking down from the exhaust port bypassing the exhaust gasket and landing on the pullstart or it could be leaking around the backplate.
Best way to tell is to clean it up, run it, and watch for evidence.
The pin - when you say it's protruding out the pinhole - is it protruding out so that it is outside the diameter of the piston - as in scratching the inside of the cylinder or is the pin staying inside the retainer area and look like it's cutting across the face of the pin and keeping the the pin from moving side to side?
First one is bad, the other for some retainer pins is normal.
2 or 3-speed - Pull rubber gear box cap off the left side.
Do you have a 2 hole or 3 hole transmission?
If 3 hole it's easy - you should see a black plastic gear through the small hole on the left.
A large metal gear through in the middle hole.
A smaller metal gear which is partially hidden by the plastic between the two large holes.
If it's a 2 hole, do your best to figure it out given the information above, but you may just be better off cracking it open. You'll probably need to do this to adjust it anyways.
BTW - noticed in another thread that your engine isn't running just right (carb o-ring air leaks). Don't worry about it not shifting until you fix these issues.
