Agree with Koda. Spark plug R&R is not as difficult as some make it to be providing you have the proper tools and time to spare without corrosion issues. A thin wall 16mm or 5/8" deep socket was essential for me to access the plugs because of the round heat shield clearance around the plugs. Also, few mention awkward access from above due to the height of the ST. Being 5' 6" I had a difficult time standing on a short stool, even with my ST being lowered 3 inches. In addition, using a THIN coat of copper or nickel anti seize on plug threads, and dielectric silicone grease on both wire boots is often overlooked. Removing the boots can be PITA due to the tight space, spark plug wire pliers will not only save the wires, but also your hands and fingers from injuries. The only spark plug I've seen used in the 4.0L SOHC without a single complaint is the recommended OE replacement Motorcraft SP-500 Finewire Platinum. CAREFULLY check gaps at 054" without touching the center electrode, and be on your way for the next 70-100K.