Is there anywhere to download or buy an Owners Manual for a 2000 Neon? Also do those Fuel Injector cleaners like (STP) really work? Thanks

Look on eBay for an owner's manual. They pop up all the time, and usually pretty cheap.

Not all FI cleaners are created equal. Look for Regane, BG44K (at your local garage, not an auto parts store), and "Sea Foam". None of them are cheap (read: $0.99), either. Expect to pay anywhere from $6-15, depending on which one you get.