Hmm are you actually trying to replace the "inventory/other" tabbedPane with the other one or are you just trying to show the new one inside the inventorypane?
Adding it inside the inventory pane should be fairly easy. You just have to put the tabbedPane with all the inventory options inside a JPanel and then include that when you make your call to add the Inventory pane.
If you are trying to replace the main tabbedPane when you select the "inventory" tab,
you should consider using something besides a tabbedPane for this selection. TabbedPane is made to switch between displayed panels/viewable objects easily, not to be used like buttons.