Using the installation wizard is the most straightforward way to handle this. You can re-run it without changing anything and it will stay the same.
However, if you just focus your changes on the IP address, subnet mask and default gateway and not change any of the others it will just be reapplied. License and password files will not need to be re-loaded because the install wizard reconize that they already exist. You should have that with you if possible... just a best practice.
What config? like your station translation on the CM side. If that is the question, yes they will stay the same. Please make sure you do a save translation to flash drive while you are at it... just a best practice.
Small downtime window? You should allow your self at least 2 hours.
Your might want to read the followin thread on TEK-TIP...
The flip side of not using the Installation Wizard wil require that you get into the G450 Gateway and change the dataside of the interface. Then you will need to go over to the S8300 side and change the IP address via a short form of the install wizard for the CM and IA770 IP changes.
What happen here? --> My experience with the wizard aren't very good to say at the least.
Hope I answered all your questions, otherwise please let me know.