You should Backup your router's settings.
Log into your router using a browser.
Depending on your router, the address could be...
http://192.168.0.1/
...or something very similar.
Check the on the router itself for the login credentials, but the defaults are usually:
username = admin / password = password.
There should be an option to Backup/export your router's settings to file.
Then if something goes wrong, you can restore the settings from that file.