Unless you're on a perfectly plain parking space, it's always advised to park it in gear. (I've experienced that the handbrake alone is not dependable).
While parking on an incline leave it in D.
While parking on a decline leave it in R.
And always have the handbrake fully engaged, to reduce the stress on gear/clutch once you get moving again.
As for service, the practice to keep warranty intact is to visit as soon as the suggested time OR kms have passed. If in your case, the time has passed while the car is still short of 1000km,just take it to the dealership and get the (good for nothing 1000km) checkup and your warranty book stamped
