Here is my 100% Achievement Guide for Guard Duty.
19 of the 20 Achievements are story related (Apart from the "Assassins Greed" Achievement)
Act 3, after dealing with the droid, watch how we get what we need lol.
Timestamps:-
Prologue - 3:05
Assassins Greed Achievement - 8:00
Act 1 - 14:30
Act 2 - 33:30
Act 3 - 1:01:40
Hope This Helps!