The coils aren't individually replaceable. You have to replace the entire coil rail as a unit, about $150 at Car Quest. I wouldn't trust one from Autochina, it may work, but not for long.
Dealers sell ones made by Standard Ignition, so does CarQuest - at about $100 dollars less than the dealer.
The ignition module is part of the PCM, not separate.
But first use a thermometer gun - the kind with a laser. Measure the exhaust temps at each cylinder from underneath. Both at idle and 2500 or so. They should all be about the same temp - around 450-500 degrees. If not, replace the coil rail.
And listen carefully - put your ear close to the coil rail - if you hear snapping - replace it.
Each coil in the rail - one end of it fires the plug ready to fire on the compression stroke - the other end of the coil fires the compliment plug (the piston on the back side of the cam) - no power from that, but it helps burn more emissions, called the waste spark. So you could say both plugs fire at the same time. It is much more powerful than the old type ignitions.
It's enough to knock you into the middle of next week! He He - don't ask!
Make sure when you put it on you use a goodly amount of silicone insulating grease on each plug - put a small glob in each boot.