Ernest Pratt (Richard Dean Anderson's character) claims to have a very strong aversion to guns. A strong aversion to guns was one of the key characteristics of MacGyver, also played by Richard Dean Anderson.
Jack McCall shot Hickok in the back of the head, not in the back as portrayed in the episode.
This episode correctly related Wild Bill Hickock's vision problems late in his life.
In history, Jack McCall was tried twice for the murder of Wild Bill Hickok. An ad hoc jury of miners found him Not Guilty in the first trial. However, South Dakota was not then a US State. He was shortly rearrested and retried in a US court, found guilty, and hanged. The court ruled that double jeopardy did not apply due to the South Dakota trial occurring outside of US jurisdiction.
Jack McCall, also depicted in the episode, did in fact murder Wild Bill Hickok. But in the episode, he's written as the leader of an outlaw gang, when in history he's reported, in his Western life, to be a buffalo hunter and then a gold miner.