It depends how the grain has been stored. If it's been kept dry and not too hot, it should be ok. If it's dry yeast in unopened packets then that should be ok, too. Hops might be ok if they haven't been opened, but are more vulnerable to deterioration. If they've been frozen or kept in the fridge, you could well be in with a chance.
Chew a bit of your grain. If it tastes good, it probably is good. If not then it won't improve by mashing it.
The recommended shelf life of a sack of properly stored grain is around 2 years, and you can still use it after that time.
So all being well, give it a go, but be prepared to change the hops. If they don't smell like fresh hops then ditch them and use some fresh ones.