What does Aristotle mean when he says, "The chief or ultimate good for Aristotle must be "final" or the "end of action", it must be "self-sufficient", it must be "complete", and must reside in the "ergon" of man"? Also, what are his arguments?

For Aristotle, the ultimate "good" has to be something that is an end in itself (as opposed to a means to a separate end). The reason for this is that, if it were not, then there would always be the endless question of "why?" A "final end of action" answers that question by re-stating itself--thereby answering it in an ultimate sense.

Thank you sooooo much! That makes sense ;)