EIGRP is modular and can be modified to work with any protocol. EIGRP did not have to be rewritten for IPv6 functionality to work, an IPv6 module was added to it.
There is no network command in the IPv6 version as it is enabled per interface and the network that the interface address is part of is what is added into the AS.
The other difference is that a router-id is required. This means that if there is more than one path to a remote router the local router will know because it can see the router-id. If the router-id is the same on both paths then the network knows that these two paths lead to the same place, this is not the case in IPv4 EIGRP. The router-id will automatically configure itself to be the highest IP address on the router. You can change it in the
ipv6 router eigrp <as> config submenu using
eigrp router-id X.X.X.X.
router(config)# ipv6 unicast-routing
router(config)# interface fa0/0
router(config-if)# ipv6 router eigrp 1
router(config)# ipv6 router eigrp 1
router(config-rtr)# eigrp router-id 188.8.131.52
router# show ipv6 eigrp 1 interfaces
router# show ipv6 eigrp neighbor
router# show ipv6 route eigrp
router# debug ipv6 eigrp