I used a single Phillips screwdriver for all of the Phillips head screws, and a single flathead screwdriver for the flat head screw.
I broke 2 of the 4 off (both on the left side) and haven't noticed any difference in the functioning of the phone.
Be sure to remove the film over the new microphone before sliding on the rubber cover! I missed it the first few times and could not understand — for the life of me — why the microphone wasn't working. It's easy to miss!