Reporting back on this, I took GlenBaker's advice and scheduled an appointment with the Decatur DMV. I did go first to the vehicle inspection bldg to see if I could turn them in there and was met at the door by an employee. He basically gave me the flip off, stating they didn't accept them there and I would have to go to the main bldg. and stand in line. I asked him what would happen if I just threw them in the garbage and he just shrugged and pointed at the main bldg. I went into the main bldg and stood in the short appt line 30 minutes before my scheduled time. The clerk at the window did accept the plates but could not give me a receipt due to the fact I had already cancelled the reservation online. She did make a notation in her terminal that I turned them in (I assume).