Where to buy display assembly or how to replace internal LCD panel?

You won’t find the LCD panel for this display or instructions on how to disassemble it, because the display assembly is the LCD panel. The aluminum casing itself is the back casing of the LCD, and the front glass on the display is the LCD itself. Even iFixit couldn’t disassemble it much more than it already is without breaking the glass. You can learn more about how the panel is assembled and why you’re stuck with replacing the whole thing in their teardown guide: MacBook Pro Retina Display Teardown

The iFixit pricing is a little on the expensive side but I wouldn’t call it unreasonable. Personally I buy displays from ProTech (https://www.protechrestore.com/index.php...) but I’m sure there are many options available.

Basically, you’re stuck with buying the full assembly :)