Door Rain Gutter on rear of 69 Dart - Rust issues

I think I agree with Furyus2. All I see in that picture is a tiny little bit of rust. For that amount of rust I would not cut the entire roof off. Now if there was a LOT more rust like that; different story. But in the one picture the OP posted, I do not see enough rust to worry about. I think I could have that cut out and patched up in one day.