In terms of food in the immediate vicinity, there are quite a few. Guy Fieri has a Mexican restaurant right there. The Harp is nearby, which was always decent, although I haven't been in years. Tavern on the Square is solid. There's a sports bar -- Banners, maybe? -- that I didn't care for (terrible hamburger, in my opinion) but my wife liked it.
What do you like for food? There are all kinds of good restaurants in Boston. My favorite is Grill 23, an amazing steakhouse, but like all Boston steakhouses, it's pricey (and isn't all that close to North Station, although everything is pretty quick to get to by T.)
What else to know... the line to get in will be long, but it moves quickly. Same thing with the line for restrooms! The line will seem staggering, but there are a ton of urinals. Lines for food can be brutal; I recommend buying any concessions before the game starts, because otherwise you'll miss a lot of action just waiting.
Where are you sitting?