Replaced my plugs last night, here's my two cents.

I have 135,000 miles on the car; book calls for 100,000. Car wasn't mis-firing, etc... so I let 'em ride. Finally had some time and was looking for a project so I went to Autozone and the OEM Iridium tipped plugs were $18 each! Yeah my reaction was whaaaaaat?!? But given I'd gotten 135K out of the originals I went for it and figured I'd never have to do the job again. Glad I did....

After taking the plastic cover off I discovered that the V6 was installed sideways and the rear bank was behind the intake manifold and almost into the firewall. The front bank was easy to do. One 10mm screw per coil and the coil came out easy. Spark plug socket was a small 9/16" so had to make one out of a spare o-ring I had lying around and a standard deep 9/16" socket (parts store has 'em for a couple bucks but I was lazy and cheap!). The new plugs were pre-gapped so no issues there. The only wrinkle in the front bank of plugs was the air intake that sits behind the radiator. Two screws and that large plastic piece came out easy, then I had better access to two of the plugs on the front. Some guys say put molly/never cease on the threads some say don't as you'll over torque. I chose to never cease 'em and just focused on not over tightening...

Now for the rear. I'd suggest checking out you tube for videos - there weren't many on JX or QX rigs but Nissan has been installing the 3.5 in all its vehicles this way for quite some time. The pathfinder was a good search. After getting some tips and tricks from there I understood the job at hand and went for it. First I took out the air filter housing which was easy as it was connected with two hose clamps that unscrewed easy enough. Then I started taking out all the 10mm screws holding the intake manifold in place (Nissan did good here making just about everything a 10mm). Next step was releasing two vaccuum hoses (use pliars for those clamps) at the back passenger side of the manifold. This allowed me to lift the manifold up and out of the way towards the air filter/battery/driver side of the vehicle. Note I did not completely release the manifold, there were a couple hoses on the rear driver side I left in place, just enough to allow me to lift it up and get access.

I went in from the passenger side once the manifold was safely out of the way. Word of caution here. Be VERY careful not to get any debris, nuts, bolts or other "stuff" into the top of your motor once that manifold is off and motor exposed! Lots of "eff" bombs will be said if you do that and a trip to the mechanic more than likely!

You will be removing the coil and plug mostly blind. You can see a bit this way (take the manifold completely off if you want a good look) but most of it is done by feel based on having done the front bank of plugs. After that it's really a matter of repeating the process, getting the plugs in and then putting the manifold back on ensuring all the vacuum lines and hoses are properly re-installed.

When I first looked at this it seemed like more than I wanted to take on but after committing it wasn't too bad. I dinked around and knocked it out in about 4hrs, taking some breaks, etc... All the part removal and re-installation was very logical and I think anyone with some mechanical know how can do this and save several hundred from the dealer. I tried to post photos but alas am not technically savvy enough to get it done. Something about the Img button and a hyperlink between the characters threw me....