I don't know enough about your study. For example, is there some reason to believe that preferences for Levels A - E of an attribute should align with their shares of occurrence in-market? For example, folks might like Level A but it may only be available on higher priced products or on less respected brands. In those cases it would not be unusual for the relative preferences of the levels to be different from their market shares (I'm assuming here that your study has more than a single attribute). Without knowing more it's hard to say whether any correction is even necessary.
Your other question is about scaling of the utilities. They sum to zero when you use effects coding of your design matrix. But other types of coding (e.g. dummy coding) are also used and do not usually result in utilities centered on zero. In fact, any additive transformation of your utilities will still allow you to use them in simulations.