Hi
I would certainly guess the resistor module is bad. Here is a link to GMpartsdirect.com. Click on "image" next to the 2000 blower motor. I think that item 25 is your resistor module, which you can find at rockauto.com for $23.
http://www.gmpartsdirect.com/partsvoice/frameset.cfm
Edit: I see the link didn't work. Enter the year/make/model. Then select AC/Heat/Ventilation, then heater, then blower motor..
Good Luck