Sorry, this will be too late for you, but gonna leave this here in case someone else searches for it. Fixed this problem tonight. Apparently, tightening up the phone fixes this (the power button unit does not attach to the rest of the phone, it merely comes into contact with the board through proximity). You can tighten the black screws on the motherboard (hard) or press hard on the upper left hand corner when taking the back cover off where the battery and sim are (easy - no real disassembly required). For a REAL and PERMANENT fix, you can totally disassemble everything and pry the tiny metal prongs in the power button area to a higher angle, ensuring that they connect effortlessly. This is considerably more difficult, but will prevent the problem from returning- FOR GOOD.
I attempted the glass-only replacement in spite of discouraging words from a more experienced tech. You will need either a hot plate or a very low power heat gun (the glue melts around 180F), you will need lots of plastic picks and scrapers. And if you wanna do it right, you will needs hours and a lot of patience. If you attempt this, keep the glass mostly parallel to the screen at all times, go really slow, and apply enough heat. I was afraid of overheating the phone, and so the glue in the area i was pulling the glass off of had not fully melted. Well, the LCD is surprisingly scratch resistant, so that was not a problem, but it will still crack. And it did. You can find a new digitizer for a little over $100. You can get a whole new phone for $200. And it will take you almost no time at all. I spent an entire day of straight work and ended up having the replace the phone anyway. Total cost was about $300 PLUS the time. SO: Unless you're a Kung-fu Master, just get the whole assembly.