If the yeast was not abused, and kept in the fridge, you should be able to revive it by making a starter. You would probably be doing good to get another yeast though, just in case. As far as the hops go, if they were vacuum packed, they should be ok.
If it's a dme with steeping grains kit then everything should go fine. If it's a partial mash kit, then you'll see a decreased amount of converted sugars from the grain, but it should be fine.
The only thing I'd worry about is if the kit was in a hot place, then the plastic bag may leave a plasticy taste on the grains.
So basically, if you open the grain and it smells fine, you're probably good to go. Just make sure you have an extra pack or vial of yeast on hand in case the other doesn't kick off.
If you're not quite sure about it, you can always make a big beer or barleywine out of it by buying a few extra ingredients.