If the fuse is good, I’d recommend checking the blower motor and the resister network.
The blower motor will be mounted on the ductwork under the passenger side dash. A Chevy dealer part guy should be happy to print an “exploded view” drawing of its installation to assist you in removing it. He can also provide you with a schematic and wiring diagram for the blower.
The blower motor will simply need to be tested. You can do this on the bench, or mounted in the ductwork using pin probes and a battery. I’ve tested them with a 9VDC transistor radio battery and they spin beautifully (if they’re good). I’ve never tried it, but I’m sure a 6VDC lantern battery would work great too, if you have one of those. The motors draw little current, and reducing the applied voltage is how the speed on DC motors is regulated anyway. If it doesn’t spin freely with a 9VDC battery, the motor is bad. Again, I’ve never tried a 6VDC battery but if it didn’t spin with a lantern battery I’d pull it and bench test it.
If you’re a bit conversant with multimeters and schematics, you can test the resistor network, but you may have to pull the controls as well to ensure that it isn’t the controls themselves. If you’re not conversant with a meter and schematic, any auto-electrical specialist shop can check this out for you. I think they’ll be better at this that the average shop.