If it has the factory unit the radio itself gets pulled out using the radio keys that are inserted into the slots on the lower edge of the unit. Nothing to remove to do that. The second diagram is the stereo wiring. The last two are what the various connection pins do with the factory system.
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.