Blown Radiator?

94 Honda Civic 230K Well maintained. About a week ago I checked the radiator level randomly and discovered that it was quite low. I added plain water as a quick fix, topping the radiator and adding almost to the max level of the reservoir. Last night, after punching it a few times on the highway, my car temperature shot way up and steam began bellowing out from under the hood. I coasted to a safe stop and opened the hood to find that the water in the reservoir was boiling and steam coming from the radiator. After drying what was wet in the engine compartment and waiting 30 minutes, I started the car and limped the final 2 miles home at very low speed. Today when I opened the hood I found that the radiator and reseroir were completely empty. I bought coolant and added to the radiator, but immediately the coolant began leaking out of the \_/¯\_/¯\_/¯\_/¯\_/¯\_/¯ that connects the top of the radiator to the body. Is there a way to replace just the top of the radiator, or seal it so that water or steam does not leak out? Do I need a new radiator? I haven't had any problems with the cooling system up until now, and all the hoses look fine. I appreciate any help.