When I do long distance traveling, to an area I am unfamiliar with, I use
http://www.airnav.com . Click on Aviation Fuel, and then trip planner. It will give you a few routes, up to 10, and provide cost of gas along the way. I did this for you, going from GFK to I40, and one of the preferred routings is GFK-OSH-I40. At OSH, there is a hotel, and nice restaurant, right on the field. It is 430 miles from GFK to OSH, and 370 from OSH to I40. I normally put in 450 as a maximum comfortable distance when I am planning on airnav.
The flight does take you across lake michigan, but it is a simple crossing, one that I have done many times.
Because Airnav is planning for low cost fuel, it keeps you away from the expensive big airports.