I.T. Help! Setting up a range extender. Comcast. Sigh.

Edit: Good grief this is a long post. I just reviewed it and it does go on. Sorry for the ramble but I wanted to add as much detail as possible.

Currently I have a Linksys dual band wireless router connected to my old Cable modem. I'm replacing the old Comcast modem with the "new" dual band gateway (AARIS TG1682G). The modem and wireless router are combined in this box. That leaves me with my Linksys, which I'd like to use to extend my WiFi signal.

In the pics below you can see my current setup and then what I believe should be the new configuration. There is A LOT of info out there on this subject and it seems a lot of conflicting opinions on how to make it work. Seems to depend on the router manufacturer, among a host of other factors, i.e. the SSID names, router channels, DHCP settings, etc, etc.

With these two brand boxes there seems to be unique issues. The link below seems to have a resolution by using a switch, which I conveniently have, but reading through this I find my head swimming. I'm not an IT pro and I'm hesitant to just shut my system down and reconfigure it without being reasonably sure I can get it back up. I work from home and as you can see, have a fair number of things connected.

https://www.reddit.com/r/Comcast/comments/42ths7/arris_tg1682g_how_to_solve_your_bridge_mode_woes/

So if I go with the switch between routers what would be my router configurations (i.e. same SSID names, turn off DHCP on x router, channel settings, IP settings, etc...)? Any assistance or opinions would be greatly appreciated!

Current setup:


Proposed setup: