1997 eclipse gst engine locked up?

i have a 97 eclipse gst. 4g63 motor. my vousin and i rebuilt the motor and being stupid and wanting to hurry up and try out my new motor, forgot put the oil drain plug back in :( . oil leaked out and my motor locked up. how can i fix this? do i just need to replace the bottom end? can i just get a crank kit and put it in? could it be something even easier like just putting the plug in and replacing the oil? any help is greatly appreicated.