With the cover removed, you will see the tops of four separate ignition coils along the top of the valve cover. Each coil has a 4 conductor electrical plug attached to it, and a single mounting bolt. Disconnect the plug (which probably requires releasing a latch), and then remove the mounting bolt. After the electrical plug and mounting bolt have been removed; the coil can be pulled upwards and removed from the engine. Sometimes rotating it slightly at first will help it release more easily from the spark plug.
I recommend just changing one plug at a time. Once the coil is removed, attach a 16mm (5/8") spark plug socket to a 6" or 8" extension bar and a ratchet. I STRONGLY RECOMMEND using a magnetic spark plug socket (sold by Snap On tool distributors) If you can't stop a Snap On truck or contact their local distributor; do an Internet search for "magnetic spark plug socket." Lower the socket into the plug well, and slide it all the way onto the spark plug. Then turn the plug counterclockwise until the threads completely disengage, and lift the plug out.
Thoroughly clean the coil assembly; paying particular attention to the plastic tube and the rubber boot at the plug end. Apply a thin layer of silicone dielectric grease to the inside edge of the rubber plug boot. Make sure the spark plug is gapped to 1.1mm (.044") and the electrodes are aligned with each other. Coat the plug threads with a light coating of anti sieze compound, being careful to not get it on the plug porcelain, insert the plug into the socket, lower it into the plug well, and start it with hand pressure, until it has turned several turns, and you are confident that it is not cross threaded. Use the ratchet to turn the plug until it bottoms, and turn it further until the gasket compresses and the pressure required to tighten the plug increases substantially (to about 15 foot pounds). Stop tightening it at that point. Reinstall the coil, and attach the mounting bolt and electrical plug.
Just be glad you don't have a Toyota V-6. What you did is child's play compared to changing the plugs in a Camry V-6.