1996 Chevrolet Corsica 3.1L V6

I have a 1996 Chevrolet Corsica 3.1L. Today I replaced the coolant as the Low Coolant light was going on and off all day. Still said Low Coolant after. Tried starting it a minute ago, speedo slowly went all the way to 120 by itself (still parked) it died and would not turn back on. Please help, I need it for work. Thank you.