Possible Blower Motor Resistor problem

The A/C on my son's 99 Grand Am was only working on the highest speeds (like 3, 4 and 5) but now it's only working on the highest speed. Does this still sound like the Blower Motor Resistor problem everyone else has been discussing here? I haven't seen any examples of only working on the highest speed yet.

If so, I have two more questions.

1. I know the part number for the part but where do I go to get instructions on how to get to it under the dash.

2. Is it possible the last speed will go out also due to this problem? If so, then it becomes a higher priority for me to get it fixed. He's away at college right now and I don't get many opportunities to work on it.

Thanks for any help you can give me on this.

The resistor block is usually attached near the blower motor so that the coils extend into the air flow. Lower speeds failing is usually a symptom of block failure, because the resistor coils limit the full power to make the motor run slower. When you get the new part, look for it bolted/screwed in near the blower motor on the firewall (under the hood). You can probably find a picture of it at rockauto.com.