I'd reccomend he change it, definitely, and it's easy to do. But he could just put another one there, as long as the terminals are clean. I did the same with my fuel pump fuse and it is fine
Again, yeah it's adviseable to grease connections... is it necessary? No. I know in my car I'm plugging and unplugging **** so often that the contact terminals are always clean
In a professioal situation and what i do to my own car are two different things. i advise the pro route, but I don't think he'll have much of an issue.