I looked at a Chevy 6.0 recently out of curiosity (just went to the car show, also saw the baby duramax Colorado), tons of real estate in there to work. You'll probably need a step ladder, a U-joint or flex-head socket wrench, and a towel or something to drape over the fender for when you lean in so you don't scratch the paint. Much easier to change the plugs on a modern Chevy small block versus a Subaru or Porsche Boxer motor (I love Subarus but really hate changing the plugs). You don't even have to move the coils. you just have a short ignition wire that I personally would change while I was in there doing the plug, but the plugs are located right between/below the exhaust ports like an old school small block. Now there's always the danger of them being seized onto the engine, but there are tools to remove the plug if it should happen to you. I personally feel having independent coils or COP architecture makes life easier for spark plug changes. Just think, you can never wire it out of sequence (unless you're really trying hard).
Iridium is probably one of the best things to happen to spark plugs. The material doesn't erode all that much compared to traditional copper and platinum, so you do get an actual life of about 100k miles between needed changes. Coils never go bad as long as the plugs are grounding well. So personally, I like to change lugs at 60k just to do it more often and ensure no plug seizure. Make sure to use anti-seize while you're at it to keep your next change simpler.
Also of note, you can't really tell if you need new wires or not, but it
I'd go for it! Get some fresh wires (doesn't hurt and might as well do it while you're in there). Get some good iridium plugs. And as to your snapping and pinging, that can be caused by octane, or bad fuel/air mixture. Some other possible causes of pinging could be the mass air flow sensor, it may need a cleaning or a new one. May also want to check around your injectors and see if any of them are leaking around the fuel rails or in their bores. Lastly, O2 sensors could also be done and not properly detecting the burn. As what most mechanics do, start with the cheap fixes and work your way up.
