With Verizon set-top-boxes, it's best to keep a Verizon router as primary. Although given the ancient Actiontec you're using, I suspect you also have ancient set-top-boxes. Those are a bit easier to get working with a non-Verizon router, but then you'll have to run Ethernet from the ONT to the router and install your own MoCA bridge. It's somewhat complicated if you're not inclined to play with networking.
I think cang_household is confused over you use case. As a replacement for the Actiontec, there is no extensive G1100 configuration required. It really is as simple as unplugging the Actiontec and replacing it with the G1100. You'll have a new WiFi network name and password, of course. You can log into the router, app or website to change the SSID and password if you want.
If you want to use a G1100 as a MoCA bridge and extender, that does require some work. But nothing in your post that suggests this is needed.
The G1100 is currently fully supported by Verizon. I've no idea how long that will last, as they just introduced an even newer router than the G3100. It could be removed from support soon, or it could last a few more years. With Verizon, we never know...
If you're concerned that a $40 used G1100 might not be supported in the near future and you don't want to pay $300 for a new G3100 from Verizon, try looking for used G3100s. If you can find one it might be a good solution.
If the dual-band 802.11ac WiFi on the G1100 isn't good enough for you, you could add the appropriate model of Verizon extender to your coax network, buy another G1100 and bridge it as cang_household described, or even put a non-Verizon access point behind the G1100 using an Ethernet connection.
If it were me, I'd spend the $40 bucks on a used G1100 and see how long it lasts. Even if it's just a year, you'll be ahead of the game. Who knows, the price of the G3100 may come down as they phase in the newer router.
