As a Porsche specialist, it takes about the same amount of time as any other car.

Make sure you buy decent disks (ATE or Brembo), Decent pads (textar or pagid), new pad wear sensors and a genuine fitting kit with new caliper bolts.

Also be prepared for the old caliper bolts to strip the threads in the aluminium hubs, as this often happens.. So you may need to drill out the old threads and fit a recoil in them (happens in about one in 20 cars, usually the front)

All the best

Jon