Hi Nithi,
I apologize for the delay in reply -- we do not at this time have a documented standard means of modifying an existing data source. As you've noted, actions in the pack include creation and deletion but not modification.
Unfortunately, writing Jython scripts for such purposes is beyond the scope of what we do here in Support, but there are two options I highly recommend:
(1) Submit and idea (enhancement request) here in the Communities. The following KB details how to do so:
How to create an Idea on CA Release Automation communities website
(2) Reach our to your CA account manager, as I think our Services team could help address your question regarding Jython scripting.