Explain to your college placement and I'm sure (Ok, hopefully) they would understand and allow you to re-schedule - if that's possible.
For the line of work you want to be in connections and 'networking' is vital, so missing an opportunity like this would be a 'bad' thing...
... and think of your CV. Doing the Foo Fighters gig can only be considered a 'good' thing in terms of your planned career - your college should support that.
OK - that's the rational stuff over with - I used to stage crew for Reading & Phoenix Festivals for about 5 years - it was awesome. Do it.
Rationality be damned - do it.
It's the Foo Fighters - do it.
