If I am reading this correctly, you wish to change who the MLS is in your DSS, correct? If that is the case, you will need to edit the MAIN_LOCATION_HOST_NAME parameter in the $SPECROOT/LS/.locrc file on the SpectroSERVER systems and then restart the Location Server process to pick up the changes.
For OneClick, log into the OneClick web page as an ADMIN user, click on the Administration -> SPECTRUM Configuration link and change the Main Location Server Name field to the new MLS. Click on the Save button and then restart OneClick.
Make sure hostname resolution is good between the SpectroSERVER and OneClick systems and the new MLS.
Joe