Seriously.....

How bad is this?

This is the passenger side rear wheel of my '69 Dart. This is the worst of it, but I have no idea how far up into the quarter panel this crap goes, it ate clean through both sides as you can see through it. I despise body work and the upper corner by the tailight is damaged. How can I effectively diagnose what needs to be done? Is this a patch panel repair? Or should I get a whole new skin and farm the work out to a body shop?

Thoughts?