If Apple is like most tech companies, they want to limit access to this kind of information only to authorized service techs, and even then they'll not get all the secrets, they'll only get the information that's necessary to complete the required tasks. I'm not saying that it's unavailable, but you're not likely to find it with an Internet search, and you won't be able to just purchase it from Apple. Any authorized service provider that wants to maintain its status with Apple isn't going to give this to you either, and I can't blame them.