if you going that far, you may as well replace the resistor
The resistor pack is essentially three resistors and a thermal fuse. If the resistors aren't melted so as to create an open circuit (fan won't run on all speeds) and the thermal fuse is still good (fan runs on all the lower speeds; high speed bypasses the thermal fuse) then there's no reason to change the resistor unit.
This photo is from my '98 Monte Carlo, which also failed the thermal fuse. I don't seem to have a photo of the resistor pack from the '97 K2500. The HVAC box "duckbill" plugged on the MC, the box filled with water, and the resistor pack electrical connection rusted so bad it couldn't be pulled apart. Everything is rusty-colored because it's full of rust and sediment.
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With the '97 K2500, I started at the 60-amp MaxiFuse, then found the HVAC fuse, at which point the motor would run on high speed, but smoked. New motor/fan fixed the smoking, but still only ran on high speed until I put a jumper wire across the thermal fuse of the resistor pack, in which case everything was good--Low, M1, M2, and High speed all worked as they should. New resistor pack--for the thermal fuse, not for the resistors themselves--and it's all back together and working good.
Of course, while the fan was out, I pushed some compressed air backwards through the Evaporator, which released a few pine needles and other leafy debris.
My fan motor had winding that were burnt black, as I said, I had smoke from the dash vents. Amazing it even ran at all. Yeah, replacing the motor and fan (they're sold as an assembly) was essential.
But if the resistor pack and the motor/fan aren't bad...why replace them?
For the record, I found with my '88 K1500 that the NAPA HVAC fan motor was smaller and spun slower than the ACDelco fan motor. I've been buying ACDelco "OEM" HVAC motors ever since. This discovery was near 20 years ago; things may have changed since then.