brokendan wrote:holy crap. seriously?
Yup, 3.5 owners (along with Nissan Murano, Maxima owners, and any other Nissan vehicle with a transverse V6) have the fun of removing the intake manifold to get to the rear bank's 3 spark plugs.
In terms of the OP's original request... the Altima is equipped with an Iridium plug and won't need replacement until 100K miles. Why change now? But if you really want to change, try sparkplugs.com. The NGK models that you can use are LFR5AIX-11 ($8.49 each) or DILFR5C11 (double fine iridium tips - $21.29 each.)