Lemme set a few things staight here.
Platinum and iridium plugs do last longer. In doing so they are a harder metal that gets much hotter than a copper plug. This means they are more likely to cause piston chipping, KR causing predetonation than a cheap POS copper plug. Which is why anyone that cares about their car will run a copper plug.
I've done literally hundreds of transmission services. The FSM states 6.5 quarts of fluid for the service you plan on doing. I've found that 7 is a closer estimation and I tell folks to automatically buy two gallon containers as it's usually cheaper in quantity. 4 quarts will not cut it and you may damage the trans running it that low.
Aluminum gaskets can be found either at a GM dealer or add a T on the end of the normal Fel Pro part number. That's the metal version.
LIM's there's really no special tools needed to do this job except a torque wrench and to ensure you have a 3/8" socket as well as a 10mm. The LIM bolts are 3/8" not 10mm as GM would have us believe.
