Here is your chance to clean the edges! Lots of gunk accumulates here.
Check the microphone cable where it enters the display. The outer layer is often cracked and this causes the microphone to short out. Wrap a single layer of the yellow tape around the area where it touches the screen metal frame.
To reinstall the two covers, hold one with tweezers, push clutch cover up. Tilt it and do the other side.
Note the wifi cable, it goes under the optical drive then comes back up next to it. You have to unscrew the back left for the wifi plug to fit through the crack.