1988 Chevrolet K3500 Heater Core Replacement

1988 Chevrolet K3500 Heater Core Replacement While removing and replacing our heater core, a clip fell out of the heating system and we cannot find where it goes as we cannot find an exploded view of the heating system. The switches no longer work and we know we have everything else hooked up properly. Anyone out there know where we can find an exploded view of this system? We certainly understand why the dealerships charge so much money for this reapir.