If you are the hands on type that likes to troubleshoot and solve your own computer problems, you might want to bookmark Apple’s Do-It-Yourself page.
https://www.apple.com/support/diy/
Pick your Mac and you’ll be taken to a page that lists all the parts Apple considers to be user installable. Instructions are easy to follow and have great up close photos and diagrams. Some older Mac instructions include handy QuickTime tutorials.