One of my legs feels longer than the other. Should I have the shoe repair guy make one heel taller?

See a specialist. The feeling of having a longer limb should be evaluated and it might not be as simple as adding a heel lift. The source could be from the feet, knees, hips and even back. The amount of any discrepancy should be carefully evaluated because over or under correction can cause more pain.
Not yet. You need to see a doctor to make sure that one leg is longer than the other. There are several things that could make it feel that way and the problem may be easy to correct with simple manipulation of your hips or back, which would be done by a chiropractor.