The ignition coils are located on the right side of the engine compartment and i recommend to replace all three ignition coil due to they were all install at the same time and if you replace only the one that has failed soon you will be replacing the other two.I would also check the ignition control module for wear and connections.
The Monte Carlo is equipped with either the 3.4 or the 3.8 liter engine. Both use 3 coils controlling two cylinders each mounted on top of an ICM (ignition control module). This assembly is at the right side of the engine compartment. Follow the plug wires to the coil/module assembly. Do you know which coil needs to be replaced?