On a 2003 Impala LS Sport, I had to replace my blower motor resister. Here is what I had to do:
1) disconnect neg battery terminal (...for disclaimer purposes only)
2) remove glove box on passenger side
3) remove blower motor and connections
4) remove old resistor, should be 3 screws. This will require a small ratchet set and I think it was an 8mm end, may also need a flex connector on your ratchet. This was a SOB to replace. The hardest hex screw to take out, you can loosen a but and the resistor should slide out.
www.Autozone.com has some great how-to's that show you in detail how to do this.