If you're looking to buy that spoiler, I have a Stillen Type III spoiler (SMZ spoiler) for sale locally... I'm only asking $175 for it (it's red and needs a little work, but that's less than half the new price of one and you'll have to paint one anyway...)
Putting eBay "performance" parts on your Nissan 300ZX is like putting Pep Boys wheels on your Cadillac Escalade... even people on welfare know better.