This ignition system utillizes COP (coil on plug) ignition, therefore there are no traditional plug wires. Insted there is an ignition coil mounted on each cam cover/ or head, they have to be unpluged and removed in order to access each plug. You will also need an extension on the 5/8" socket to get down in there. The Labor guide estimates approx 1.6 hours to do the replacement if you've never done it before and 0.5 if you have experience on it.
If you have replaced plugs before on traditional type systems, This should be no different for you. Another piece of advise I can give, always remove the spark plugs with the engine completely cold, otherwise thermal expansion of the plug and head can distort the threads, making installation difficult, but this caution should be observed on any plug replacement. Also, I like to use a 3/8" x 1' piece of fuel hose to put onto the ceramic portion of the new plug, then use it to install them, before using the socket to tighten. The flexability of the hose, will allow the plug to go in straight and not cross thread, since they're somewhat deep into the cylinder. If you would like assisstance while attempting the job, feel free to ask, or if you still have difficulty locating them, send me a pic of the top of the engine and side of the heads, and i'll point you in the right direction. My e-mail is RIP180OUT@aol.com
Thanks, XXXXX XXXXX the pics. If you can send a couple more pics of in between the cover marked "Vortec" and the valve covers. GM has used a couple of different locations for the plugs, the first is inbetween the Vortec cover and the valve covers, and the second, is below the valve covers, on the side of the head. Also, remove the Vortec cover, this will make it easier to view the top of the engine.