two routers on LAN

Ok …no laughing here. I have a core router (UNIX)on my LAN that is responsible for all routing , DHCP and DNS. This box is getting old and I`m suer it`s going to fail sometime soon. What I would like to do is setup my Novell server to do all the routing and DHCP and DNS ( currently a secondary would convert to primary ). I realize I can`t have two DHCP servers so I wouldn`t turn that on until I removed the UNIX server for service. What potential problems are there going to be with two core routers on the same LAN ?? I