Starting Over

Want to start over from scratch and replace my Medicaomm Cable Modem. It has to be located in the basement of a 2 story brick house. Have an Ethernet cable running from it up to a back hallway office modem where I plug in a printer, laptop and security system into the box. I need to keep the office the same with the ability to plug into, but that is where the Wi-Fi signal is broadcast from. Need to update this 5 year old system which now has smart TV and 5-6 devices pulling from it all the time. Also want to be able to access the security camera system remotley, the current set up does not allow that. Suggestions please. Thanks.