Should he change crankset or cassette??

[Andrea]

Can you clarify what you mean by "attack" hills?
In racer-speak, that generally means that you're going hard up a hill in order to put other riders into difficulty. In that case, his gearing is fine, and he should work on his fitness.
If you mean that he wants to make it easier to go up the hills, then a compact crank may not be a bad idea. He can get a 12-27 cassette and keep all the same parts otherwise, but it won't make a huge difference.

Oh yeah- and if he really does want to "attack" hills in the racer-sense, then he can still do it with a compact crank. The only place where a compact can hold you back is if you want to haul walnuts down a decent or sprint faster than ~35mph.

[SouthernBelle]

Haul walnuts? I needed you at my house this fall!

I live in a hilly area and ride a triple. I'll never be Queen of the Mountain, but over time have improved. I wouldn't be in too big a hurry to swap if he has only been riding a short time, especially since he hasn't ridden a full season.