you don't have to set the dhcp to google, but I have lol.
the easiest way to test, is connect deco to hub as steps 1 & 2 above and then if you have something normally hardwired to hub, plug it into deco instead and see if you get internet. That should work basically out of the box. If all good, set sid/password on deco and try to connect a wifi device, you might need to disconnect wifi on say your phone and then reconnect but shouldn't have to if you've used the same sid/password as you did on hub. If that works then the deco's are working, now you can set dhcp as required. ie some of my devices have been assigned an IP address, so I know my zgemma is always 192.168.0.123 etc