Hi, the four week check is just so that the dealer can make sure that nothing is leaking or has come loose. Your engine oil only needs to be changed after the stipulated mileage or after 12 months whichever occurs first.
This 4 week check thing is just so the dealer can check your car over. It's not mandatory. I didn't have it due to buying my car from a dealer far far away. However I will be doing my own service at the 6 month point.