The breaker is behind the right side panel. The oldest pdf format I have is 1990 but it should be the same as the 1988. They use the same body style and system. Click the link below for the location of the breaker and relay. To get the switch out it requires some instrument panel pieces to be removed and can get quite involved. The heater relay should click once the blower switch is turned on. Does the switch feel abnormally loose when sliding back and forth?