I am supposed to get my keyboard replaced, what steps should I do before bringing my laptop in?

Perform a last Time Machine backup to a mounted external drive that is formatted to either HFS+ or APFS (either implicitly case-insensitive, journaled). Don't bother with encryption as that is the great slow-downer and worse if you forget the password.

This way, if the operating system gets replaced during the keyboard replacement, you have the means to restore your own data and previous configuration later.