with an immersion chiller, you really only need to worry about the outside. Vinegar will do the job as well a few other cleaner/sanitzers. I use PBW and Starsan. I sanitive before I put it into my boil. It is overkill, but it puts my mind at ease.
Primary 1: Oatmeal Coffee Stout
Secondary: American Mild IPA
Keg 1: English Bitter
Next up: Double IPA for friend, Kolsch, Graff, American Wheat, Dunkleweizen.