Again odds do not figure into it, only certain chemical reactions can occur, Helium is never going to react with oxygen but Carbon reacts with many things, it's no accident that life is composed of the most common molecules in the universe and they react in ways that are not governed by chance...
Those are not the only "modes" do a little bit of research, http://www.talkorigins.org/ would be a good start.
Again not true complexity can indeed arise spontaneously, google is your friend...
http://www.talkorigins.org/faqs/thermo/probability.html