The already replicated data won't be re-transmitted, but we recommend that you create a new target container for the new replication, in the same storage group as the old target container. You can break the old replication, but don't delete the container, so that all the data is in place on the target. As long as the new container is in the same storage group as the old one, the data will be deduplicated. So you can create the new replication with a different source. The repication will sync up on name space (meta data etc.) but the actual physical transfer/sync-up will be minimal.
Once the new replication is INSYNC of course then you can delete the old containers.