Plugs are a bit harder on the VQ40DE than your ol' VG motor. You have to remove the coil packs to get to them; four of them aren't too bad, but the front two on the passenger side are under the intake plenum and are a real pain. Technically, you are supposed to remove the upper plenum, but it can be done, painstakingly, without doing it. You need a good assortment of tools and some patience to do it without plenum removal. Don't quote me, but I think the labor guide time is around 2.0-2.5 hours. The spark plugs aren't cheap, either. The factory plugs should be NGK OE Laser Iridiums #93759. Online you will probably find them in the $20 per plug price range. If you are looking to save a little money without losing performance, you can use NGK Laser Platinums #6240, which was the plug originally used in the 05-07 Pathy. Like the OE Laser Iridiums, it also has a 105,000 miles service interval and can be found online in the $10 per plug price range. I did this in my 08 model and performance and gas mileage stayed the same. I would use nothing but those two plugs and if you have a shop do the job, make sure they are using the correct NGK plugs, as well. This site can give you estimates for your area:
www.repairpal.com