Here is our fuel price calculator. I would use at least $4/gallon for your calculations, and add 20% to the point to point mileage. Use the average gas mileage for your vehicle, not straight highway mileage. This should cover it. Gas in Chicago is above the national average and you can safely use that number in your calcs.

Lodging, figure an average of $75 a night using "budget" accommodations. Food - you should be able to figure that using what you pay for groceries and restaurant/fast food meals where you are at now, those figures don't vary much no matter where you are. Staying in hotels that have free breakfasts can help here.