This is actually a very revealing bit of dialog because it reflects that Michael was not in the Family business at that time--even said (after the bandleader story), "That's my family, Kay, it's not me." "He's a good lawyer" is Michael's opinion of Tom's professional qualities--Michael, the former and about-to-be returning college student at that point. "Not a Sicilian, but I think he's gonna be consigliere" is Michael, the family outsider, reflecting on a decision his father will make that has nothing to do with him.