Hello Laurie,
There will not be an impact to the business outside of the ring duration for users changing on non-ACD (queue) calls. As soon as the change is made on this side, users will see the ring duration on those calls change to whatever you requested it be set to.
The ring duration for ACD calls can be set by clicking on the name of the queue under Admin->Contact Center. The Resource Center article that outlines how to set this is at the following link under "Edit queue behaviors and thresholds for voice channels".
https://help.mypurecloud.com/articles/modify-existing-queues/
Thanks,
Chad