I have an uncle that contracted Guillen-Barre in his mid-late 50's. He started feeling gradually weaker, until he couldn't get out of bed one day. Went to the local hospital, where they were testing him, and kind of diagnosing him (they weren't sure), for a stroke. After 24 hours, my cousin transferred him to the Cleveland Clinic.
Within another 24 hours, they had an accurate diagnosis, and had started treatment. They were able to predict the course of the disease almost perfectly. They said he would get progressively weaker, more difficult to breathe, and would require a ventilator just to breathe. All of that came to pass. He was in the hospital for a month, and in intensive care for about a week (from what I remember-this was about 15 years ago)--later he told me the ventilator was the worst part of the whole disease. They also predicted recovery, but they couldn't predict the extent of the recovery, or the timeline with nearly as much detail as the progression of the disease.
He did eventually recover, but for him, it was a long process--sounds like it was similar to what Schlereth went through.
Prior to the surgery he was physically very strong--had worked in an auto factory putting 95 pound bumpers on vans every 90 seconds. He had built several houses, renovated a couple more, and helped various people in our family with roofs, and additions to their houses. After the surgery, he still planted a huge garden, but never took on construction projects again. I don't know how much of a factor age was, he was something like 57 or 58 when he got it, so he may not have done so, even without getting sick. I don't think he was ever quite as vigorous afterwards, but it would still probably count as a full recovery.
I don't think it ever recurred with him.
It sounds like Frederick has a mild case (prior to this I didn't even know there were such things). I am not dismissing anything with this disease. People that say his career may be over--they could be right. Likewise, people that say he will fully recover in two or three months--they may be right. Who knows? Nothing would surprise me here.