GM CHAIRMAN and interim CEO Ed Whitacre Jr. has aggressively been cleaning house, leading some to wonder if he’ll go too far. The General’s middle-to-upper-management bench is very deep, though. And so far, Whitacre seems to like managers in their early to mid-40s, men and women barely associated with the Roger Smith years. His best promotion thus far has been to name Mark Reuss North American president. That makes three car guys close to Whitacre, along with vice chairman Bob Lutz and board member Steve Girsky. Lutz’s role still hasn’t been formally described…Fast-rising star Susan Docherty, GM sales, service, and marketing veep, has named Brian Sweeney as Buick-GMC general manager. Sweeney, 42, replaced Michael Richards, a Ford veteran who left as general manager of Lincoln-Mercury in 2008, reportedly over arguments…