Classic story: iPhone (without a case) fell out of pocket onto the pavement and front glass was shattered. Screen protector in place and held glass together.
All went well except the new 'button' doesn't work well. Takes multiple pushes to work. Having the screen protector on meant I could haul the glass out in one piece with a suction cup.
Without the screen protector holding the glass fragments in place, removing the glass would have been a real mess. I tried removing the glass from the 'frame' (heating the adhesive) so I could just order the glass alone but I warped the frame. I would skip even trying this and just order the "assembly" (glass + frame) instead, even though it is more expensive. Save yourself the grief!
The connectors for the screen, button, speaker, LCD are very tiny and required patience to reconnect. Don't lose your patience and force them. If aligned, two should 'snap' into place and the third 'clamps' when you move the latch mechanism.