The plugs are good up to 100k and come pre gapped most will opt to change them at 50k. I doubt you'll have that many miles so rule that out, also it's a PIA to get to the coil packs to get the plugs. The injectors are fine as they are, And you don't need to touch them unless you're upgrading to FI. Take the time to read your Service Guide this will give the basic maintenance recommendations. Have a Great Day
http://www.nissanusa.com/pdf/techpub...2010_N_SMG.pdf