Caporegime
Are the teeth in the top of the mouth or the bottom? If it's the bottom you're ok, they inject into your gum and all you'll feel is a tiny scratch. If it's in the top then you're screwed, they'll inject the roof of your mouth which is absolute agony - think of that scene in Marathon Man.
Nope, the placement of the needle depends on many factors and you most likely won't feel much pain. Slightly uncomfortable for a brief second or two but not pain.
You'll be fine