Should my mechanic found a permanent solution?

What is your question?

05 Nissan Quest alternator failed and needed replacing. Mechanic diagnosed faulty radiator as well and replaced both at $1200 cost. Immediately after the vehicle emptied new-radiator-full of coolant and the new alternator failed. Instead of diagnosing and repairing the coolant leak (that didn't exist before his work), instead of locating the leak source, he used quick sealant. Now the same leak is back and he wants to charge more to fix a problem he caused. What are my options?