Hi Thom,
You can use the Delphix CLI to discard your existing replication spec. You can find the procedure on how to do this on our help article
"CLI Cookbook: Deleting a Replication Spec". From here, you can reconfigure your replication profile, as outlined in the help article
"Configuring Replication".
Please note that this would only delete the replication spec. If you would like to free up space, you should go to the dSource in question and delete it.
I hope this helps. If you have any questions, please feel free to let me know.
Thanks!
Srish