Excerpt: One day after Marsh & McLennan Cos. ousted its chief executive, the nation's largest insurance broker said it will tell its clients exactly how much they are paying for its services and renounce back-door payments from carriers. The move, prompted by an investigation by New York Attorney General Eliot L. Spitzer, could help spark massive changes in the notoriously opaque insurance market. The key questions now become how far the scandal will spread,[.]