I’m afraid I’m not very familiar with netbeans, so I can’t help you there.
Typically, panning is done in JGo using scroll bars. However, if you want to implement a panning operation where you use the mouse to grab and pull the diagram, you’d need to define a new mouse state for the JGoView and override doMouseDown, doMouseMove, and doMouseUp. A mouse move after a mouse down would change the cursor and call JGoView.setViewPosition.
You'll need to figure out if you want this to be a separate mode (i.e. the user can't select or draw a new link) or modeless (i.e. disable rubber-band selection but allow other mouse behaviors to work).