There is a ton of information available on Apple’s websites. The problem is to find the right document or hint when you need it. Three places to start digging are: Apple’s manuals for their hardware, the official site for technical information or the Apple how-to video section. You may also want to check out iFixit if you need to upgrade or repair your Mac.
Mac users who want to upgrade or repair a Mac find all the necessary information at ifixit.com. The site offers extensive repair guides for most Mac models and iPhones, including many pictures and a list of the tools required. The manuals are free and there is a vibrant community helping with troubleshooting and answers on all sorts of related topics.