I called Garrett today. I was told that my detector is on its way back today. She said that they replaced the internal electronics on the control box as well as one of the coils that I sent in. They also tested it with their calibration equipment.
Looks like it's going to be nice enough to get out this week. I hope the weather stays ok where I'm at. I've found where the fairgrounds were in 1900 here. I'm sure the area has been cleaned out thoroughly, because I've hunted the area a little bit myself already. The place where I hunted might not have been quite the right spot, so I'm hoping they did a superior job in fixing up the detector. That's the spot I'll be hitting when I get it back.