1) At the time of husband's death the nikah remains until the completion of iddat e wafat. Therefore the wife can give ghusal (bath) and coffin to her husband . But the husband becomes na mehram for his wife on her death.
2)After her husband's death, the wife can see him, she is permitted to give ghusal (bath) and coffin to him according to shariah. Likewise after his wife's death the husband can see her face and he can give shoulder to her funeral. If the woman has no mehram relatives then the husband can put his wife inside the grave though it is not permissible for him to touch her body and give her ghusal (bath) and coffin.