When we upgraded, only the modem was replaced. We kept our PVR (recordings intact) and other boxes (one wired, one wireless). All other connections remained the same; no access to the boxes or other hard wired devices needed. So basically just a swap-out of one modem for another.
Don't know what your current phone system is, but this upgrade will force you off the copper line and onto VoIP.
Samsung Smart TV | Bell Fibe | Apple TV 4K | Pioneer 919AH | Panasonic BD75 | Bose AM6