:Pull the lower panel below the glove box to get at the HVAC unit. The fan assembly simply unbolts or unscrews from the bottom (three I believe, been a while since I did mine). The fan and motor simply pull down and out of the car after unclipping the wiring connector to the motor. :You have some debris that got into the fan and is clipping the edge of the blades as it spins. In my case, a mouse had built a very large nest in the middle of the fan over the winter.
As for the AC not working and the mechanic's screw up ... check your fuses to see if any of them didn't care for the current reversal.
