Use tape to hold the connectors out of the way.
Okay, is the side with the soldier joints or the side with the capaciters the “face?”
Also, you need to destroy that little hook that keeps the big connector on unless you have three strong little hands. Don’t worry, it’s not going to fall off, you can still cut yourself trying to wiggle that thing off. Especially when you are holding the board by the edges to avoid the “face.”
The microphone gasket is not really a gasket like an O ring, it is a foam box into which you insert a little metal box on the end of the ribbon cable. Be sure you look at the side of the foam box that faces the bottom of the phone. The wider margin is towards the Lightening connector. The metal box goes up into the bottom of the foam box forming an “L” to the bottom of the phone. It is easier than it looks.
Never saw any gasket for the headphone jack.