I really enjoy casseroles. I like tuna, and I love tuna noodle casserole. I am not a fan of sour cream and I would not put it in when I make it, but the recipe sounds great regardless. I like flavorful tuna recipes. I have been known to add tuna to macaroni and cheese, with the addition of chopped tomatoes and calamata olives. Mmmmmm....
As for the metal scare I am aware of it, but I don't eat tuna more than a couple of times a month, if that. I don't consume very much.