Radiator "tubing" rust. How much should I pay to replace. Coolant leaking.

Hello, On that one, it will depend on which components must be replaced, and if you have rear heater lines. Also, once in the system, they might find something that needs attention as well, such as heavy systemic corrosion buildup. I would recommend you get multiple estimates for the work, and ensure you are using an ASE certified facility/technician.