How long has your scar been? How big is the area, how is it caused, what is the state now, is there a large area of uplift or is it just that the color is different from the normal skin color?
20-year-old scars are hard to get and no longer obvious. Surgery is to change obvious scars into inconspicuous scars, and it can't completely remove scars. Ask the plastic surgeon in the hospital to see if it is necessary to have an operation. From your description, I don't think it is necessary to have an operation, really.
If there are bumps, you can do microcrystalline dermabrasion surgery. Some people say that the photon instrument in beauty salons can remove scars, but it has not been verified.