Processing time on the Canadian side usually doesn't take more than 5 minutes or so (but there are exceptions during peak periods) processing on the US side is highly variable and can be as little as 5 minutes or as long as 45-60 minutes. I would plan on 20 minutes in heavy, post-game traffic. The tunnel entrance is only 5-6 minute's drive normal traffic from Ford Field, once you are on the street.
Re Windsor, the Detroit-Windsor Tunnel would be the route to take (do NOT use the Ambassador Bridge), if you wish to visit Windsor. Farther still (walking not recommended) is the Motor City Casino. The Greektown Casino is within comfortable walking distance of Ford Field and the MGM Grand is walkable, but farther away.
Re casinos, there are 3 of them in downtown Detroit, so it really isn't necessary to go to Windsor unless you have a special interest. There is a fair amount of parking (lots and garages) near Ford Field as it is adjacent to Comerica Park, the baseball stadium for the Detroit Tigers. For the NCAA, however, expect heavier traffic and allow extra time to find (and pay for) a parking spot. Almost the entire trip is freeway driving. In 'normal' traffic, you should be able to drive from Dearborn hotels (Dearborn Inn, Hyatt Regency, Ritz-Carlton, Doubletree) in 15 minutes.
