This is an extremely helpful guide. I was quite surprised when I opened my iPhone 5 that there were 2 screws lose inside it. I bought it new and have never taken it apart or had it serviced before. Never heard any rattling either so who knows. haha
I noticed that needed the smaller Phillips head screwdriver than the one recommended in the guide.
The only advice I can give is to take your time and go slow slow slow. There were many small heart attacks when prying the screen off and taking out the battery.