stock plugs are good for what you have.... start adding rockers or a cam, headers.. etc.. then you want to step down to a colder plug such as the autolite 104`s. you are fine for now,...
gapping plugs means that you set the gap between the electrode and the pickup (the regtangular wire that hovers above the center electrode). you can change the distance or "gap" between them. this allows for a hotter more effcient spark depending on your application. an effective gap is about .054-.058. Gap always depends on the type of plug, mods you have and how you drive. there really is no set gap to use... you have to tune the gap to your application.
to answer your question... yes, you have to gap your plugs anytime you replace them.
