For ignition parts please, please, stick with Nissan parts! The aftermarket parts tend to cause more trouble than the savings (if any) are worth. I order my parts from Joe at
www.everythingnissan.com - best to call at 1-888-216-5328. They're one of the sponsors of this site (or have been at some point).
You'll get a discount (wholsale) and know that you're getting the right stuff. Joe is a great guy to work with and can help with all kinds of useful information. I'd go ahead and replace wires and factory plugs at the same time if they haven't been done recently.
Heath