Check out the link below. Pelican has detailed the steps in doing it. I did mine last month with the front wheels. I removed the hubs and have a friend with a hydraulic press in his garage pressed out the old bearings and installed the new ones. I am sure you can find some shop in your area that has the press. Pulling it out with a puller with the hub still on the car is easy but installing the new one is a bit harder to center and making sure not to misalign the two inner races. Otherwise, it's a fun weekend project.
Pelican Technical Article: Boxster Wheel Bearing Replacement - 986 / 987