Unfortunately, Yes! Once that brown stuff starts traveling in old galvanized pipe it's all over. Replacement is the only solution short of bottled water. And with the real estate disclosure laws, you'd probably have to fix the pipes anyway in order to sell the home. The only advice we can give is to get your money's worth from the plumber you select to do the work. To do this, have each plumber submit a drawing of what pipes he will replace and what size pipe will be used. At least you will be able to compare apples for apples. And, by the way, replace with copper and the problem will not come back.