I know this is late bit a trick I use to put the standoffs in (had to do 2 cause someone lost the screws I was replacing) is to take the screw that goes in it srew them together loosely to give it a fake phillips head then gently screw both into the spot the standoff goes in. you can then take the phillips out (may need to put a spudger between the screw and standoff to keep the standoff down then use a tiny flathead to gently tighten the standoff down. its a few steps but makes life easier if you need to replace it quickly.
It is part of the face id part so yes. This is the ear piece too so if the ribbon tears there is a chance the ear piece will stop working as well.
I want to point out that in order to do this step you have to remove the screw holding the CD drive in place first. On top of this if the screw is out very light pulling on the drive will remove it. There is no need for a pry tool or a needle to eject it. To make it easier on yourself I would actually do step 5 first and just be done with all the screws before you take out the CD screw (Which, by the way, step 5 is shown with the CD drive still attached and screwed in which can cause confusion and possible damage if not careful/paying attention).