For the first time in 26 years, Hinshaw & Culbertson LLP has a new lawyer at the top.Donald L. Mrozek has stepped down as firm chairman, a position he has held since 1989.Vice Chairman Kevin Joseph Burke has succeeded him.“I think it was just time for me and the firm to transition while I’m still healthy and able to assist to make sure everything continues to go well,” said Mrozek, 68.The firm’s partners approved the move in November. Though it wasn’t announced until today, Burke, 58, became chairman last month.“I …