95 Chevy Cheyenne heater/AC vent airflow problems

I am looking at buying a 95 Cheyenne 1/2 ton PU truck with 135k miles. Truck is in descent chape, but when attempting to change heater/AC airflow from vents to
vent/feet to feet to feet/defog to defrost, airflow either doesn't change at all or takes minutes to change.
Is this a simple repair? Or is it a major dashboard removal all day affair? Also, the fan doesn't run in highest speed.

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