I have an '01 grand prix with a gunked up radiator. What should i do to keep the car running well?

I bought the car used recently and its runs fine and doesnt get too hot. I know this problem has something to do with whole dexcool/ regular antifreeze issue but i dont know if i should flush it and use dexcool or just regular antifreeze at this point. 82,000 miles on it.