Easiest way to get into the car is to push the remaining piece of the key
into the lock and then turn it! The lock should hopefully still open as it
will still have the 'whole' key in the lock.
As for replacing the key, once you are in take the door apart, remove the
lock aand take it to a locksmith and they should be able to remove the
broken piece, then make a new key (or even rekey the lock).
A.
