You will need to find a friend with a tuner, or buy a tuner, before you even start collecting parts for a top swap. It's required, and that's also where you will find the most power, is in a good tune.
I would stick with the same kind of spark plugs you have now, which should be iridium.At least until you start putting boost into the engine, that's when you will need colder copper core plugs. Also, stock plug wires are really the best bet in terms of longevity, there's not that much improvement to be made, and there are few aftermarket wires that can compete with the durability and reliability of factory. Of course, IF you want to change up the color go for it. lol
Also, the thermostat won't change anything if you go to a lower temp, all it will do is set off a CEL and you really won't see any cooler temps than 200 regardless of thermostat temp.
Everything else is a definite go, lol the only real upgrades you will need is once you do the top swap: headers to keep the KR monster away, a shift kit to keep the trans happy, and a tune to keep the engine from eating itself. Then, if that's not enough, you could go full blown racekar and do a cam, rockers, intercooling and E85. Or turbo. lol
All of the stickied threads are your friends, read all of them multiple times. They will answer most of your questions before you ask. like I do.
