Answer to: How do I replace the glass only?Presumably similar to these LG G3/G2 glass only replacement video, as LG G4 lcd construction is very similar to G3 and G2. https://www.youtube.com/watch?v=H0dxMv5-Fds&t=87s https://www.youtube.com/watch?v=QrxIWVaM...
Answer to: Hair dryer for logic board reflow?Actually I would make an argument against using a general purpose heat gun to reflow a motherboard. It's easy to exceed maximum temperature of component and fry everything using a high powered heatgun, where as it's much safer to use a hair dryer, which cannot generate too high a temperature. Of course, electronic quality heat guns are different story, as these allow temperature to be controlled precisely. But this is just a warning from my experience of frying multiple motherboards using a general purpose heatgun, despite constantly monitoring the board temperature with IR thermometer. I even physically melted a bga chip down, even though my IR thermometer never indicated temperature above 160 degrees C!! So extra precaution is in order when attempting to use a general purpose heat gun for reflowing motherboards without fine control over temperature output.
Answer to: No Power, Not ChargingI had same issue with my macbook air. No boot and no charging. SMC reset didn't work. Unpluging charger and heating with dryer didn't work either. The solution was to open it up, unplug the battery from main board, wait half an hour and I could boot macbook. I noticed that battery was already 40% charged when it started up again, so macbook not being able to start was not due to low battery. It was due to some kind of crash or soft malfunction which entirely prevented macbook from booting until battery was unplugged from motherboard.