Water leak caused by rot at hood hinge cavity....

[DieselHead]

Greetings,
I've been battling a light to moderate water leak in my driver's side rear foot well and today discovered that it's coming from a nickel sized hole caused by rot near the driver's side hood hinge. I took it to my body shop and the guy refuses to touch it. He told me that to do it right would be extremely expensive and would require cutting through body panels. I understand that it may be difficult but part of it may have been that he doesn't want to bother. Regardless, I'm left to deal with this myself.

Has anyone else here ever had to deal with this? How do I remove the surface rust that is there? What should I use to patch up the hole that's there now? Tar? Expanding foam?

Thanks for your words of advice. I want to fix this as soon as possible so that no more moisture gets in the body panels.

Alex