Murph, if I understand your application correctly, you basically want to extend your LAN with a wireless switch?
If that is so, all you have to do is connect everything on the LAN-side (do not touch the WWAN). Assign an unused static IP address so that you can always talk to the switch and turn off DHCP.
The Ethernet switch is independant from the router. If you disable DHCP, the clients will receive addresses and default gateway information from your primary router.
Agreed. Turn off DHCP on the 2nd switch. Let the first one assign the addresses. On some routers this mode is called bridge mode.
