First of all, congrats for taking the leap into racing!

Accommodation:
Some people arrive the night before, some the morning of. Personally, I'm always there the night before. I would rather wake up at the track than wake up super early and drive to the track.
Most people camp out at the track for the weekend, there is plenty of camping space and it's included with your entry fees. The bathrooms and showers at GBM are good, the main one is even on city water. Some people who aren't big fans of camping get a hotel in Grand Bend which is 5 minutes away.

Food:
They have food there, which is actually pretty good but they are only open for lunch and breakfast. You are better off to pack a "food" cooler and use freeze packs that don't turn into water when they melt. Then you need your "drinks" cooler...lots of water, energy drinks, beer...whatever. If you have the 2 separate coolers your food is not in danger of getting soggy from the melting ice water. Even if you don't have a BBQ with you, likely one of the people you are pitted beside will have one and usually won't mind sharing some grill space.

See you at the track!