Just changed my sparkplugs to NGK iridiums too. I check the old plugs and they were a bit worn after only 45k miles. Took my about two hours to change the plugs for the first time, and it was not complicated at all, you get the hang of it after the first 2. You just need to make sure and have at least a 10" extension for your ratchet. Also when you first insert the plugs, make sure to screw them in by hand first. If you strip the threads, you're F**CKED. Then torque them to 20lbs with a torque wrench. My acceleration is much peppier and the engine has no more knocking that it had previously, so they did make a nice difference. Don't forget to put anti-seize lubricant on the first 5 plug threads before screwing them in.

 

nice info!