Five hundred hours is what most people consider "Low Hours" on any Case or Ingersoll GT. It as you say, it has been well-cared for, then the engine should not need to be rebuilt until some time after there are 2000 hours on the clock.
If you own this tractor, then just keep it. The replacement value is more than eight grand today for a new one. About all you will get for the 4014 is around $1200.00 but that figure will vary depending upon where you live.