I want to test a new modem but possibly go back to the old one. Can I do that without problems?

I have a Netgear CM2000 modem there may be an issue with so I want to try with another modem. I got a new Motorola MB8611 modem I would like to try on my gigabit Xfinity connection. If I install the new modem, test if for a few hours and then want to go back to the old modem, will that be a problem? With my current Netgear modem I did not need to call or do anything just provision it with my computer. I assume it's the same with the Motorola modem. But after having provisioned the new modem will it be a problem to re-provision the old modem again? I do not want to end up without Internet for hours so I thought I would ask her first.