My iPhone was only charging intermittently - it would take five minutes each day to find a position in which my phone would charge. This led to my phone running out of battery and my becoming a social pariah. I fixed it because my phone was out of warranty and I didn't want to pay Apple. I'm also a bit reckless when it comes to tech - my fingers never break electronic equipment.
Well, the first thing that happened was that I managed to break the camera out of the phone using the phone screen as a lever. That was pretty worrying. After much disassembly and worry when it came to the battery, I managed to put the new stuff in. I hadn't kept the screws sorted and in fact lost one, so now my screws are in position by the maxim 'if it fits, it's ok' and there's one too few holding the screen connector bracket in place. I'm sure it'll be fine.
Segregate your screws by size so you know where to get them. Don't cheap out and do buy magnetic screwdrivers. There's a big magnet in the camera and reinstalling screws near it with a non-magnetic screwdriver is just a pain in the neck, takes ages and all kinds of 'noooo i'm breaking my phone!!'