Network connections..?

Need some serious networking expertise...

My house came prewired with 4 Ethernet ports. I currently have FiOS service which lets me to connect a device to every Ethernet port and get a different IP address for each one, without needing a router or modem.

My desktop PC (no WiFi) is connected directly via Ethernet. On another floor, I have a WiFi router connected to an Ethernet outlet for my laptop and cell phone.  Even if I connect a WiFi dongle to the PC, the WiFi signal isn't good enough to cover all 3 floors.

The ISP is "upgrading" their service but that means only one of my 4 Ethernet ports will remain active. They say I could install a router in the communications panel in the garage with at least 4 Ethernet outputs to connect all 4 outlets inside the house but they'll have to share one IP address.

That means the router in the garage would be hardwired to a WiFi router inside, and hardwired to the port connected to my desktop.

Seems pointless to put a second WiFi router in the garage because I'd never use its WiFi. Can somebody recommend a non-WiFI router with at least 4 Ethernet ports that's relatively easy to install and maintain?

Do I really need a router or would a switch be sufficient for this purpose?

So much for their "upgrade"...  :emotion-12: