Well I based it the fact that you said you got a IP conflict when you changed your router to 192.168.1.x for gateway, so that made think your modem was already giving the router a 192.168.1.x for WAN. As long as your modem's and router's gateway are different, it shouldn't cause a conflict. Then you just router 192.168.0.1 to 192.168.1.1. Your routing the gatways, not the IP the gateway's are giving out.