Based on the serial number, it was manufactured in 1989. However, it was manufactured late in the year it could be a 1990 model. Both years used SunTour XCD but only the 1989 used the Sakae branded crank, so it should be a 1989 model. A Mint Celeste finish would warrant a small premium over the Sierra Blue finish but we'd still need pictures to assess the condition and subsequent value. If you want to maximize your return, you may want to consider waiting until the autumn. It's my experience that this is the peak season in college towns.