It does not appear that Gene finished college. In August 2012, on the 21st Gus announces Gene is the first person in the family to have graduated. On August 23rd he is discussing with his parents that he is going to skip his graduation. On September 6 & 7, 2012 we learn that he has 5 hours to complete which he can do in one semester. After that there is the wedding and farm. I do not think he ever completed his 5 hours.
Try http://www.gocomics.com/arloandjanis/1998/03/13