And about the force...listen to Ben and Yoda, they told you everything you need to know, and they didn't contradict each other either.
It's an energy field created by life and binds the Galaxy and everything in it as an interconnected system. Even rocks have the force in them and have connections to everything else. This field is something that can be sensed, tapped into, measured, and otherwise studied by beings who are sensative to it. This field also 'controls' everything and everyone despite being mutable to the whims of individuals. Future events are shaped by the force and patterns can be sensed to predict likely outcomes, and these patterns in the force can be manipulated again by force sensative beings. It might be said that sentient life is the conscious expression of this energy field.
As far as the midichlorians go, I guess they allow life to tap into the force and use its energy to produce effects. Instead of one specific organ able to manipulate the energy it's lots and lots of organelle-like structures found in all life...how it got there, who knows. I'm sure BKL, with his exhausting, uh, I mean exhaustive knowledge of the EU can shed light onto the mechanisms and characteristics on the midichlorians.
Of course there's also the dual nature of this Force, but that's another topic.