The power/lock button on my wife's phone quit working. The Apple guys at the mall wanted $200 to fix it. I ordered the power/lock button and tools from iFixit.com for about $40.
While wife and daughters were out celebrating the grandson's birthday I had time to open up the phone and replace the button. But that wasn't the problem. More reading at iFixit.com and I found that there was supposed to be some kind of spacer between the button and the micro-switch. One of the posters said nail polish worked. Step daughter brought home a bottle and after a little painting on the bottom of the button I had a spacer. Put the phone back together in less than half the time it came apart.
Read the posts. There's bound to be someone else with same problem you have. The tear down was pretty easy for me. I've taken apart my Dell laptop a few times. The parts are a bit smaller. But have to take same care with the parts. Watch out for the flex cables. You CAN flex them too far. I LOVE the magnetic mat. Did a great job keeping the itty bitty screws from getting lost.