Engine won't crank 1999 Monte Carlo

1999 Monte Carlo I bought with 103K miles and drove 15K pleasurable miles in 6
months with regular oil changes and fluid checks.  Coolant began to leak within in 3
miles of my home, temp was okay and then started to overheat slightly above normal
as I arrived home, car puttered once as I pulled into driveway.  I let the car rest a
couple days, topped off with proper amount of coolant, but engine would not crank (only
once did it spin for a second or two.  Had battery checked, it's fine.  Are the pistons
having a tough time?  Gasket?  Manifold?  thanks