In real life, Elder Dalton would have been sent home from his mission when he had brain cancer. No missionary is ever allowed to stay in the field "just because he wants to," particularly in life-or-death matters of health like that.
Many things that Elder Allen needs help learning are things that are taught in the the MTC (Missionary Training Center in Provo, UT). It is rather obvious that the character has never been. All missionaries, both Elders and Sisters are required to attend the MTC before being sent to their assigned mission.