Hey Rick! You can toggle the background image in the Lights palette. Just click "Background" and then click on the thumbnail of the texture and choose "Texture Off". The background image will stay loaded in your palette, so you can toggle it on again for rendering purposes. As for turning ligjtcaps on and off, I don't know of any way to turn them off other than turning the intensity to 0 as you said, or pressing the Del button in the lightcaps subpalette which deletes that light entirely.
Pushing buttons is probably one of the best ways to learn Zbrush. I've run into some of my happiest accidents this way.
Hope this helps!