Spark plugs won't make a noticeable difference =\
it may make a difference on a turbo car because of how rich our engines run, but on a car like yours, it's not worth spending the money. You might get 0.2hp out of it lol
EDIT: it's a really easy install, if you don't mind spending the time. it actually doesnt take that long ... anyway, you unplug and remove the coils from the top of the engine (remember which one goes on the left and right and where the connectors are, or your engine will fire the wrong cylinder at the wrong time hehe), use a long ratchet to unscrew the sparkplugs from the car, drop in the new ones and tighten em up. not too tight though, you dont wana break it while its inside the engine