What should my father do to prepare for his upcoming immigration hearing?

I am writing on behalf of my father, who is unsure of how to proceed.My father was born in Canada in 1956, and within three days of his birth was brought to the United States as a resident alien. He lived and attended school in the Metro Detroit Area, graduating high school in 1974. He received his Associate’s degree from a community college in 1975. He lived and worked consistently in the metro Detroit until 2009.He has two children from a previous marriage, one 13 years old and one over 18, who are both US citizens. His ex-wife has custody of his youngest. In 2006 he remarried to a Canadian citizen. He moved to Canada from 2006 to early 2010, when they separated. They now plan on divorcing. Upon their split my father wished to move back to the United States, but his green card had been revoked. He has no close family or connections in Canada, and wishes to return to the US. He is currently living with his mother in the US. My father is an intelligent man, but lately has suffered from some cognitive impairment. From what I know, he’s been diagnosed with multiple sclerosis, which temporarily caused him to go, for lack of a better word, fuzzy. He is trying his hardest to work through this set back, but becomes confused and has trouble thinking ahead.As he has been out of work for a year, due to both illness and work restrictions, he does not have much money to work with. He does need a lawyer, however, for his court hearings (some approach rather rapidly now). He just recently contacted me and told me about his situation – apparently he has had hearings already, but he’s unable to tell me what went on.My question is: What should my father be doing in order to prepare for his upcoming hearing? Does he need a lawyer to proceed?