The 6 plugs are located on each side of the V engine. 3 on each side, you will see 3 black wires on each side, they are for igniting these plugs and twist them before you try to take them off or they may be hard to pull off. After you take the wires off unscrew the plugs. One at a time. Look for the rusty exhaust on each side, the plugs are mounted in holes just above those two exhast manifolds(they are called). A special 13/16ths spark plug socket is used, along with a ratchet and extension. All 3/8ths drive will do. Put some spray lubricant on the threads to make them easier for the next time. Some spray silicone helps the wires come off easier the next time, and easier to install also. A 3.9L correct? RN12YC Champion plugs are the best plugs, and are installed from the factory. Ok
You can use a piece of quarter inch rubber fuel line to hold the plug to start it in the hole. They sell the plug starters as special tools at the auto store. They have good instructions here and all the tools at the same auto store you buy the plugs at.