Just want to share this in hopes it might save people some time in the future. I have an 08' GS and my AC would only work (green light) on fan setting 1, higher than that and the fan would work but no AC or green light. I've seen this before in another vehicle and figured it was the resistor, got the replacement instructions from this thread.
Everything went smoothly until that damned last screw on the left of the resistor. I probably spent over 2 hours trying to remove it with a small screw driver, scraping my hand up quite badly. I gave up for a day, picked up a small ratchet at the store and tried again - still failed.
What did it for me was removing the other electrical component that's to the left of it and closer to you, part of the fan I think? It has two screws also, the one further from you is also extremely difficult unless you do it this way: Take out the screw closest to you, unplug the connector, and push the component up/away from you - it will turn on the axis of the second screw until it is exposed. Then you can unscrew that one and remove the component, leaving you with a lot more space to get at the resistor. When you put the fan component back, do it the opposite way - put in the second screw first while it's tilted up, etc.
I'm not really a handyman or a mechanic, but I was able to fix this and have cold AC again. It just took me longer than most here. I hope this tip will save someone some time and frustration!