How can I replace the spark plugs on this car?

Hi kiwii, Here's the instructions on how to replace your spark plugs. 1) Remove the air filter, and associated rubber fittings. 2) Use an "L" or "allen wrench" to remove the decorative engine cover. 3) Use masking tape to mark front three plug wires. To access the rear plugs, you have to remove that entire intake and throttle body assembly (silver looking portion on top of engine). 4) Detach the throttle cable, and cruise control cable. 5) Remove wiring harness plugs from throttle body. 6) Disconnect fuel lines from throttle body, and injector fuel tubes. 7) Use a bigger allen wrench to remove tight bolts holding intake manifold to the engine. (this is actually the air pflenum, to be exact) 8) There are two more hex bolts to remove, on the back side of throttle body. 9) Disconnect any other ground straps, or connections not mentioned above, so that you can remove intake and throttle body as one big unit. ONLY NOW can you see the rear cylinder are of the engine. 10) Label the back three spark plug wires, for future reference. Since it's so hard to get here, you may want to just replace the plug wires, and distributer cap, for good measure, to help things run OK. 11) Carefully pull out the spark plug boots/extensions, which stick down in the engine head / valve cover tubes for about 6 inches (15 cm). 12) Find the spark plug socket which fits your new plugs. Attach a 12cm or longer extension, and ratchet. Remove the old spark plugs. 13) Use the socket and extension without the ratchet, to put the new plugs back in the holes, so you can more accurately feel the threads. 14) Re-attach the ratchet, and tighten the plugs. (under 20 ft lbs) do NOT make them as tight as you can pull, this can cause damage. 15) Put your wites back on the correct plugs. You should hear/feel a slight click/snap to confirm that the contacts are on plugs properly. 16) Re-assemble everything else you have taken apart... Good luck!

Thanks so much Dvigano, looked like it's so complicated but I will try the steps as you suggest. Kiwii

My husband and my daughter replaced 3 spark plugs but can't get to the 4th spark plug due to something melted around the spark plug. Can you tell me how to get the black substance off so I can remove the 4th spark plug? Attached a photo of it.