Munny's Character

Is Munny really a good person? Several times throughout the film, Munny repeatedly states that his wife set him straight. However, despite this, he goes off to kill, some guy he's never heard of before. Munny is a premier example of moral ambiguity.
When we first see Munny, we see some grey-haired old man trying to herd pigs. He falls into the mud several times, further emphasizing his feebleness. Two seconds later, we figure out he's some cold-blooded killer bandit. At first it seems that he has changed, but when the Schofield Kid arrives and tells him about the reward money, Munny begrudgingly accepts. He grabs his partner and gets onto his task. Before they even reach their target, Munny and his partner start to converse. Munny talks about how he's so different from before, and how his wife helped him with that. While you can assume that Munny is talking to Ned(Morgan Freeman), you can tell that he's really talking to himself. Its like he's trying to console himself, convince himself that he never, ever would do any of that again. However, the fact that he willingly went out to kill some random guy and leave his kids with a woman that hates him for weeks on end, leads me to believe that he might not be all that good himself. Munny claims that he is only doing it for the money, for his kids, yet there is probably some hidden agenda inside him that wants to kill again.