Aside from the VIN number, 10th digit, which in your case should be either W or X for '98 or '99 respectively, the easiest way to tell is by reading the underhood emmision sticker. It will tell you which model year standards your vehicle conforms to, and is considered one of, if not the, most official designators. At least by the state of CA for smog/registration purposes.

Those who have posted before are correct that the door date is date of manufacture, which can vary quite a bit from model year. The Manufacture date is important to the Feds for safety standards and the like, but is not a true indicator model year.

Check the VIN, it's quick, easy, and dang near never wrong.

MV