Mike Turk is an excellent coach, and had much success prior to coming to Illinois. Unfortunately, when you have to suffer fools, it is very difficult to be successful.
As for a replacement, the obvious choice seems to be Bob Olesen. Since it is highly unlikely that Jerry Clayton will consider coming back, Bob should be the head guy. He has produced as a head coach in a big way, grew up in Illinois and was an outstanding triple jumper for the Illini, and was a member of the team during their run in the late 80's when Wieneke led teams won six Big Ten titles in a row. He knows how to win, has won, and will win should Ron Guenther have enough sense to hire him. On top of it all, he is great guy.