My brake pad light just came on at 30,000 miles and it looks like it's still got quite a bit of pad left on both front and back at around 5-6mm. A few questions:

1) how many mm of brake pad left should I drive until before I change out the pads and rotors?

2) while I'm doing the pad and rotors changes, is there something else I should do at the same time (like brake fluid)?