Heater Blower Switch

How hard is it to change the Heater Blower Switch on a 93 Aerostar? 3l. When it is running... sometimes the amp guage will drop and I can smell wire burning. When I turn off the Heater Blower Switch it will stop and the charge is ok. It is becomeing a problem when the switch is on high. Cold weather and all. But did not have this problem till it got cold and switch was on all the time. Any comments will be appriciated and any knowledge is accepted. Really don't want to pull the dash out to get to it if I can get away with it, and I don't have a garage to work on it.:screwy:

It sounds to me more like the heater fan motor is starting to bind?? If so they are cheap at the recyclers and not that dificult to change.