How do you replace the evaporator on a 1995 gmc vandura 2500?

To replace the evaporator on a 1995 GMC Vandura 2500, start by disconnecting the battery and draining the refrigerant from the A/C system. Remove the dashboard and any components obstructing access to the heater-A/C unit. Unbolt the evaporator from the housing, replace it with the new unit, and reassemble everything in reverse order. Finally, recharge the A/C system and test for proper operation.