AWK Find and Replace

I am new in awk and i want to replace a whole line. Its a part of the hardening script.

in /etc/pam.d/system-auth i need to change some configurations entry:

so there is a line called password requisite pam_cracklib.so

and it needed to change to password required pam_cracklib.so ...

So i thought i try to find first if there is already the line password required before i replace it, but i can not find the right way.

How is this been done, maybe on a different way???