How do you know when the brakes need to be replaced on a 1999 Toyota Camry and how much should the job cost for both the front and back pads and rotors?

When the linings are about 1/32" or so. The cost of replacing a part is a very general question that unless specified exactly is hard to answer. First, is who is replacing the part? Is the Dealer, an independent repair shop, a junkyard, the guy next door or you doing the replacement. These will all yield different prices. Not to mention that within all of these will be different labor rates and different part price mark ups. Second, what is the quality of the part? Is it a name brand, generic (white box, economy), OEM or used part? All of these will be different. Price will even differ between name brands, sometimes significantly. Thirdly, What is the warranty of the part and who is offering the warranty (the shop the parts house or the manufacturer). Limited Lifetime will have restrictions. Lifetime warranty isn