All right! After watching the Patriot and Buccaneer game, I spent 2 hours to replace the plugs, take the car out for some test driving and a little grocery shopping. After I came back, it was exactly 12 AM. Glad that I did not delay it to the next day. The old plugs look very healthy. I tried to take pictures, but the lighting did not do justice to them. So I shall take some pictures tomorrow during day time.
I am also happy to notice that my odometer is actually at 88k miles, instead of 89k. I am very glad because I indeed noticed A BIG DIFFERENCE before and after the plug change. I can totally tell that the car now starts quicker, runs more smooth, and has more power. Seeing is believing. Currently the car's display shows that my average is 17.6 over about 8k miles of driving. This is pretty low, still reasonable b/c my wife is pretty much 80% driving around schools, shopping and in parking structure of her office. When we first got the car 11 years ago, she got 17.3. So probably have not waste too much gas.
Also I spend 2 hours b/c cylinder No. 3 is a b*&#^. I got all the other 5 plugs done in 30 minutes. But the last one is very annoying. I did use a lot of 3/8'' extensions and u-joints to get this one done. So be prepared if you want to try this.
Finally, I must recommend this tool to beginners.
https://www.amazon.com/GearWrench-80546-8-Inch-6-Inch-Swive/dp/B0014ZVSVK
It literally took away all the pains and hassles. Life is so much easier with this tool. The benefit to cost ratio is HUGE.
PS. I think I can tell the difference b/c J37 is a performance engine. I replaced the plugs on my ancient Camry with Denso twin tip iridium plugs not so long ago after 55k miles but 10 year. I couldn't tell any difference at all. That engine was designed 25 years ago, I guess any plug will be good enough for it.