Carbon or ceramic pads are the best...I did the pads on my 02 at around 42k, two months back. There were no sensors on the pads to indicate that they were low. I just felt the trac was not stopping or slowing down fast enough when I applied the brakes.
If it is just the pads you are doing, you can do them yourself. I did mine. Just make sure you have jack stands as additional support to the jack and a C Clamp to push the pistons on the Calippers back in, along with a good set of socket / rachet tools.. Search the projects and posts, you will see further instructions on how to do the job.
When you are done, you will have the greatest feeling in the world. Just take your time and double check everything. Remember brakes are not to be taken lightly. If you are unsure about your diy skills, take the track to a brake specialist. They should be cheaper than the dealer.
PJ