The lock button on my iPhone suddenly wouldn't click the button. Apple wanted 150 to fix it, so I figured I'd fix it myself for less. Much less.
Following two different guides was a bad idea. I ended up with four extra screws (which I found out that later held the front plate to the metal frame, but it's still held in place by six other screws anyways) and removing three others to help with display issues and a battery problem (that I caused by accidentally switching up screw sizes). All in all, seven screws still not in, the iPhone is working great. I put in two layers of really small duct tape pieces (1 mm square) over the physical button to help the contact between the button and the lock button.
If your device is out of warranty, fix it yourself. Worst case scenario, you break your device (I was due for an upgrade soon anyways) and you learn about the innards. Best case, you save yourself oodles of money. If a college student (like me) can do it, you can too! Be careful with your screws. I used a tray with many compartments to sort mine. I wish I had known how tiny the screws are. They're like REALLY small in the iPhone.