Totallynew, although you are fit as a runner, you still will have to get accustomed to cycling... it's a different ballgame. As for the type of bike, that really is just a matter of personal preference. I commute on various types... folding, fixie, MTB, road, vintage type roadster so there really is no 'right' bike for commuting. Do you have a shop nearby that offers bikes for hire? You could give the various types a try and see what feels best to you.