Yeah, the mileage and few mods are not going to bring serious 'collector' attention. You still have a very desireable lower mileage car that will appeal to many. With excellent condition ultra low mileage '99 Anniversary cars bringing prices north of $20,000 I would tend to believe that your car could fetch in the mid teens. $14,000 - $16,000 would seem to fall in line with the prices the other cars are actually getting. Let's face it, a regular similarly equipped '99 low mileage T/A would be in the low teens (KBB shows around $11,000 - $12,000 in my zip code) so an 'anniversary edition' would almost have to be a few grand more, unless your car has had numerous owners and Carfax or title issues. That would hurt the value. Unfortunately for proper pricing guidelines, you have some owners asking stupid prices for average cars. They see those $20,000 prices and then think their higher mileage, average cars are GOLD. It makes it tough to properly gauge a correct price point. The pricing I suggested is for a 'real world' sale, maybe, not wishful thinking.
** Yes, definitely fix things when selling. Selling with repairs needed is a big negative as 'lookers' will wonder what else is wrong and perhaps think the car was neglected. Human nature. When I just sold my BMW Z3 I fixed a very simple minor issue that cost $130. That cheap repair eliminated any problems with the car and any questions a 'looker' would have. Well worth it. I sold the car within 2 weeks at proper pricing levels.
2001 Trans Am Convertible Red w/ taupe top (A4)
2007 Ford Mustang GT/CS Convertible White w/ black top (5 speed)
1974 AMC Matador X Red (3 speed auto)