How do I fix....cold air on drivers side, warm air on pass side. W

What is your question?

-Coolant level is fine, flushed out heater core diretly, installed new thermostat still no change? -Both the mode and Blend air switches are manual(cable)and everything from the outside looks and sounds good. How do I get out the large box that houses the mode and blend doors to see whats going on inside? Are their any online manuals that could help me?