I won't put in any kind of radiator leak fix gunk - I did that once before in my Dodge Shadow and it fixed the leak for only a month or two only for the system to blow out pretty bad when I was far away from home. That crap is terrible to put in your cooling system anyways.
I've not noticed any hairline cracks in my radiator. There is a funny looking vertical cap looking thing behind the radiator cap..? I don't know if that's removable or not.