In the early 1970s, Life Master Andrew Karklins was one of the top 400 players in the world. He has about twenty wins against grandmasters, including one against five-time Russian champion Peter Svidler. A few months ago, Andrew beat GM Jaan Ehlvest, who peaked at #3 in the world rankings.
If Chicago's Lakeview neighborhood (not too far from Sheridan and Diversey) is convenient for you, you couldn't go wrong by taking lessons from Andrew! His rates are ridiculously reasonable.... Drop me an email if you're interested and I'd be happy to pass along his contact info.