You can use any hard drive you want that is 3.5" in size. You could even use an SSD if you wanted (normal 2.5" drive). Though you may need to use to some double sided tap to hold it in.
The cable that goes from the Power Button, down the side to the volume and hold buttons, then to the interconnect board has been torn/damaged. This requires replacement. There are 2 places where you can easily catch the cable and rip it. http://d3nevzfk7ii3be.cloudfront.net/igi... If you look closely here. You will see the cable go over the frame twice. I have made this mistake enough to not make it again.
Generally whenever I see this there are 2 possible solutions, once of which is not cool: 1) The LCD requires replacement (cross your fingers this works). 2) The motherboard in the phone has a bad fuse or something. This requires replacing the board/phone. Is the phone under warranty? If it is, then that is likely the easiest way to get it fixed/replaced.
I am a computer enthusiast and well seasoned ACMT (Apple Certified Macintosh Technician) at a local repair shop. I love building and repairing computers, overclocking, gaming, beer, and a good laugh.