The concession stand at Oswego is one of the best around. Decent prices and good food (though, the typical concession stand variety). Despite the fact they no longer sell Hoffman Hots (Boooo!), they still have decent hot dogs, very good fries, pretty darn good (but smallish) pretzels, and outstanding huge chocolate chunk cookies (though lately they've been more chips than chunks). I haven't tried anything else, but they do have burgers, I think chicken fingers, some specials, the usual. If the other items are as good as what I've had, you'll be fine. Just get in line early before a game or after a period. They can get long.
They do have some tables outside the rink proper and a lot more tables downstairs, if you want to sit and relax. Obviously, you could go out, but you're talking at most two hours between games. Less of course if there's overtime.
As for a nice place after the game, I'll let the locals answer that. There are some good places, I just can't recall them offhand.