Q: Is there a way to change the title of the item's header ? How about gaining access to the panel's contents ?

A: All these elements of an AccordionPanel item can be accessed through code. For example, in case of an event dispatched by an item of the accordion panel, the component passes an event object. This object holds a reference of the item that dispatched the event. In this case you would gain access to the title text field and panel content like this:

eventObject.item._header.accText - this is the header's text field (the item's title)
eventObject.item.content - this is a reference to the content loaded into the panel

The attached example shows you how to make use of these elements.
Files: AccPanel_AccessData.zip