I need a painless way to commit suicide?

I want something like a gun to the heart that is quick, but I am too scared of the pain to fire. I am considering jumping off a bridge near my house, but it is always crowded and I'm too embarred to do it publicly... That's another thing. I want to be sure that it gets no news coverage. What would be nice is if I could write my family a note saying I've left and then disappear somewhere no one will ever find me when I do it. Or, make it look like an accident perhaps? Either way I also want my family to collect insurance. Destroying my body would be a bonus since it complies the most with my wishes to be cremated. Any educated ideas? Sleeping pills are my first choice, but I'm so confused about the quantity I need to be able to go instantly. Please help?