How much disassembly do I need to do to get to it?

It does slide from half way all the way over to hot but it will not go from half way over to cool. In fact even at half way or all the way over on hot it still feels like the air temp is the same. I think its rusted or blocked also.

Even with the blower in the off position it still blows light heat out.

Why would it not shut off completely when the blower is shut off?

When the blower shuts off is there a flap that should close to completely close the air from coming in? I have never fiddled with any heating lever system

If on the e-way in the off position it blows like its on low speed even though its off completely. My guess is the air is flowing enough at speed to cause the fan to rotate a little and make it feel like its actually on?

Anyway could you briefly explain the easiest way to get to that lever assembly under the dash so I can repair this?