Since a single coil on one cylinder was previously replaced; I assume your Sable has individual coils on each plug. These are very easy to replace. The coil is held in place with one bolt; which must be removed, and there is a wiring harness plug on the top of the coil which must be disconnected. Once that is done; the coil can be pulled up off the spark plug. Sometimes rotating it slightly will help break the seal friction and make it easier to remove.
If the new coil comes with silicone dielectric grease; use a screwdriver blade to spread a thin, even layer of this special grease along the inside edge of the rubber boot on the bottom end of the coil. Then press the new coil down onto the plug, install the mounting bolt and connect the harness plug.
The spark plug in the # 2 cylinder also would need replacing if it became fouled because the coil has been misfiring. A long extension attached to a magnetic spark plug socket, or a plug socket with a heavy rubber insert which securely grips the plug can be used to take the plug out. Be sure to use the same brand and model of plug as the one which was in the motor
The trouble code will need to be cleared from the computer's memory with a scan tool that has code clearing capability, after the repairs are completed.
That's all it takes!!!