I wouldn't replace anything until you find out why it's overheating. Guessing isn't the way to fix anything. I would check the coolant, fluids. Run the car until it gets hot, when it starts to overheat check things like the fan, leaks, tstat opening (both hoses should be hot if open). Etc... I wouldn't go replacing rad, or flushing things out or whatever until you know what's causing a problem.