Countrywide Financial, the nation’s largest mortgage producer and servicer, abruptly announced late last week that it is replacing its president and COO. Significantly, the management shakeup comes at the same time Countrywide’s two-year-old dominance of the mortgage industry is starting to show some strain in 2006.On the management front, Stanford Kurland, a 28-year veteran at Countrywide and one-time heir apparent to co-founder, Chairman and CEO Angelo Mozilo, was replaced as president and chief oper-ating officer by David Sambol, a seasoned executive who observers called more polished and dynamic than his predecessor.