Customizing WPF Expander; Make only icon clickable not whole header

Question

I want an Expander that only expands/collapse it's content when the user clicks on the header icon. (Instead of the whole header being clickable.)

Do I have to redefine the control Template to do this? How would it look like?
Where can I find the standard templates/styles for controls?

Thanks for your time.

Answer 1

I posted a solution to my question here (same link as in the comment from Ben).