How is the refrigerant charge?
I doubt that I’d worry about those fins, much less want to take the dash down to replace it unless it’s leaking refrigerant.
For the loss of blower speeds 1 and 2, disconnect the resistor and see if you have 12V on the pins (yellow and tan wires) when 1 and 2 speeds are selected. If you do, then swap the resistor. If you don’t, check the connector at the blower switch on the panel. Wiggle the connector to see if the fan kicks on. Some of its pins may just be bent or something. If it’s melted or damaged (leaving a black residue on the blower switch pins) the connector can be replaced. You can either clean up the blower switch’s pins or replace it.
If that connector is burnt and the blower has rust on it, check for a leaking windshield cowl vent screw directly above the blower in the intake. It lets rain into the blower housing and floods the passenger carpet.
You must be registered for see images attach
You must be registered for see images attach