This is actually a computer I sold to a friend. 1 week after the fact he called and said it wouldn't boot, there was a folder with a question mark icon. He took it to another friend who replaced the hard drive, for $100. That hard drive "failed" also. This all sounded fishy to me.
I got the computer back and was able to boot the computer from the original HD with a SATA to USB device. The HD was in good working order.
I did a search for MacBook Pro HD failure and found the flex cable could be the culprit. I replaced the cable and the computer booted right up.
Question: How do these things go bad anyway?
The repair was not horribly difficult but there are a lot of small pieces and small connections. You either need a magnifying glass of good close up vision.
3 things were not completely clear in the instructions:
1: In step 14, the ZIF lever was difficult to understand because the image is so small (the part is too)
I thought it popped off but it just flipped up. Read the directions carefully.
2: I wasn't quite sure what this comment was referring to: Many fixers cover the length of the thicker cable in the pair with sections of electrical tape on both sides because it can rub the tiny ridges inside the aluminum case causing a short to the case itself or simply breaking the connection.
I didn't do anything
3: There was no guidance on how to and how much the cable should be bent to follow the contours of the case.
I bent it just enough to get it to fit.
Even with these questions/problems, I was able to successfully compete the repair.
You can do it just have the right tools and patience. Good eye sight and good dexterity help as well.