Step one: Take compressed air and clean the entier top of the motor, dont want any crap getting into the engine.
Take a 3/4" wrench (I think, maybe 5/8"), and loosen the injector lines at the injectors. Move the injector lines out of the way, dont go bending them like crazy though. A little movement wont hurt though.
Take a screw driver and pop the black (or if they are stock, grey) plastic caps off the tops of the injectors (the things with the rubber lines going between the injectors). They will just pop off.
Take a socket and remove the injectors. Make sure the copper washer comes out with the injector.
Take new injector, with copper washer (only 1) and tighten down into head. Go snug but not crazy (like 25ft lbs?, nothing crazy). Take your NEW return line kit (because you did buy an injector return line kit), and find the rubber o-rings. Each injector gets two. Its rather easy. Now take the return caps and pop them onto each injector, making sure they are seated flush. After all that is done, take your hose (you have to cut to length), and put the pieces in between each return line cap like it did stock. Dont forget the little green clamps that come with the kit.
Now place the injector lines onto the top of the injectors. Make sure you get them back to the right angle (because you will have to bend them just a little to get the injectors out, remember, just a little) and get them threaded onto the top of the injectors. If done wrong, the injector threads strip and you need a new one. You will know if its right or not, little resistance.
Do not tighten down the injector lines all the way, leave them a little loose. Go into the cab and crank the engine for about 5 seconds. Go back and you will see each injector has fuel at the injector lines. Tighten the lines down. Start the truck.
And done. Good luck!