How do I replace the power button

@platinumchisk that sounds like a power button flex issue since it still works sometimes. Since iFixit does not yet have a guide for this, use something like this video to at least get you close to it. You will have to take the screen off as well to get to the flex. A lot of times it will be easier (and more expensive) to repalce the complete midframe since the flex will be on that.The flex cable is readily available at many online stores.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.