After a few years of giving others a hard time about dropping their iPhone and breaking their screens, I did it too, even with a case on it. I am mechanically inclined so I decided to do it myself and do it right.
The on-line tutorial with excellent pictures was great. I bought a container with 26 compartments and numbered each one. As I removed the screws, I color coded the heads the same colors as the circles on the pictures, using a permanent marker. I then placed the screws in the compartment that corresponded to that step in the process. It helped a lot sorting out all the different length screws when they are so small. It took me about two hours total and it works great.
Take your time. When I received the new screen it had the blue protective layer on the back of it. When I removed it just before attaching it, I noticed it had several pieces of white stuff on it. I used a lint free cloth to brush them away only to have them smear or scratch the back of the digitizer. Not sure why the "dirt" was there, but I thought the thing was ruined. It hasn't affected the graphics yet so hopefully it was only superficial. I suggest peeling back protective layer and inspecting your digitizer before starting this process. The attached picture is how it looked before I wiped all the stuff off. It was located between the digitizer and the blue protective layer.