I have been riding my first road bike for a couple seasons now, and am starting to get the itch to upgrade some of the components. I have a 2010 Specialized Secteur Comp with a Shimano 105 gruppo. I have already upgraded wheels and tires so I am thinking of stepping up to a Ultegra or DA crankset.

My current crank is a compact Shimano FC-R600 with BB, I have no idea what size BB this is.. What is all involved in changing cranksets? Can I upgrade to either Ultegra or DA without changing any other components?

Thanks!