1998 Ford Mustang Apparent Fuel Starvation Issue

1998 Mustang GT. Recent tune-up, new plugs, all new wiring etc. Seems unrelated, but my car just stops, then won't start if I let fuel level get below certain markings. At first, I could go down to approx. 1/4 of a tank without problems. But once there if not refilled, the car would just quit (feels like fuel problems). Once fuel added, tank refilled car would start fine, then run fine, as long as I stayed above 1/4. Now the problems occurs earlier. When I reached 1/2 reading I would have the same situation. Now, I can only let it get down to about 3/4 before the problem arises. Again, it just stops running (seems like fuel problem), once I add gas and refill then it runs fine. I would like to know your thoughts on the problem. What major replacement parts might be needed, and approx. How many labor hours would it take a trained, certified mechanic to repair. I will take to my local gas station, who has worked on the car for many years, just want to get 2car pros thoughts ahead of time to understand what the problem and expense might be.