Replaced 1, 3, 5, and 7 on mine a few weeks ago (3 was the one causing the engine light). Removed tire and fender liner so I could get to them easier. Did not disconnect the batteries and reset the code myself with EFI Spade Jack, but any autoparts place can reset them for you. I figure I'll replace 2, 4, 6, and 8 when one of them goes out.
2007 2500HD CC SB Classic 6.6 Turbo LBZ. EFI Live DSP5, MBRP Turbo Back Exhaust, MBRP Turbo Downpipe, PCV Reroute, S&B Cold Air Intake, Alligator Transmission Cooler Lines, Ready Lift Leveling kit, EGR Blocker Plate, Firestone Airbags.