More than likely the blower resistor is bad. Following is the procedure for replacing it. Once you get it out you can look and see if any of the wire coils are burnt.
I believe that is it, the rivots may be whats holding the resistor coils to the mount. can you stick a screwdriver in between it and the firewall and pop it out like the instructions say?
In the meantime i will try to find a picture of it.
I'm sure that is what it is,,here is the wiring diagram with 5 wires going to it.
It may be that one of the coils is broken and keeping it from coming out.