Have a look at this page. It explains how to setup master-master replication. The memcached-repcached add two more options to the official memcached options which are:
-x < ip_addr > hostname or IP address of the master replication server
-X < num > TCP port number of the master (default: 11212)
It should be easier to setup master-slave replication if you want.
For your question about running memcached and memcached-repcached on the same port. You don't need to run the original memcached daemon and modified memcached-repcached daemon at the same time. If you want to use the replication feature, you don't need to run the original memcached daemon.
As a general rule, it is not allowed to run more than one service (daemon) on any specific port number on the same host.