Yes it would be possible.
Yes it is a bit of a hassle if you don't know what you are doing.
You'd basically need to set the second router to have exactly the same SSID, and password as the main one, then change it's IP address to one that's different to the main routers subnet and switch off DHCP on the second router. then connect them together via the home plugs using the LAN ports on both routers. (not the WAN port)
Although, if you say what the exact model numbers of the routers are you may be able to set them up for WDS.... which is designed to do exactly what you want automatically.