The expiry date on most things has a little bit of "margin" built into it so you are probably fine. But yeast does loose viability over time so you certainly didn't get the best "bang" for your buck.
Did the beer turn out OK? Only one way to tell and that is to take gravity readings at about 10-14 days, bottle it when it is done, and taste it. If the beer tastes OK and your gravity readings are OK then you are OK. But regardless of the outcome I certainly wouldn't buy any more kits from whoever sold it to you.
Cheers!