I understand that it's free right now to do a cancellation of an itinerary. Is it also free to do a change?

The reason I'm asking is because there is a return leg that I want to change my itinerary to. But I have an outbound leg that I don't want to lose and it doesn't show any availability anymore on AP.

I'm not sure if I should take a chance of canceling my whole intinerary and then just hope that the outbound will get put back ton the search results?