how do I confirm if the blower motor resistor is my problem?

It needs to be installed in the blower case in order for the air blowing through the case to cool it. Never tried it outside the case , don't know how long it would take to cook. To see if it is still functioning , unplug the blower motor connector and measure voltage across the two terminals. should be battery voltage with key on and fan set at high. Should decrease as you turn the speed setting down. To test the blower motor jump battery voltage across the blower motor terminals (2 sec. max.)