So... to troubleshoot - replace the resistor ("transistor") first?

I doubt BOTH the fan motor AND the resistor pack are bad....

You can test the fan/blower motor by just jumpering it to a 12VDC source and spinning it...

 

If it's the blower, i recently bought a new blower online for under $40
It was a 10 minute install
Replace the air filter after same time