If you really want to get into pulling injectors then go to an auto parts store and pick up a basic repair manual - Haynes or Chilton's for about $20. It will tell you how to pull the fuel rail and injectors. It will also tell you how to check the electricals. (The most straightforward thing to do btw is just to swap the #4 with another and see if the misfire follows the injector.) While you're getting a manual, inquire about a fuel line disconnect tool for GMs.
Before you go get into all of that you might just run through a shop (or find a buddy with the right tools) and have the compression checked. Ruling out mechanical issues first is never a bad idea.