Here is a quick DIY for replacing the final stage resistor on a 2000 328Ci.
First, I bought the new resistor from Pacific BMW for $62 including delivery (UPS).Loren Wong- Pacific BMW (E46 userID- USCTrojan4JC). You will also need a Torx screwdriver set.
Once you are ready to start, you will need to remove the 6 screws holding the glovebox. The glovebox should just slide down and out easily. Then disconnect all the light harnesses to remove it completely. Next, remove the remaining plate with floorboard light.
Looking into the console, you'll notice the duct in front of everything...
Don't worry about the duct. It's flexible enough to work around (but TIGHT!).
You will be able to see the final stage resistor behind another component. There are two torx screws (T20 if I remember correctly) holding this component in place, remove the first one as shown (shown removed).
The second screw is accessible from above the component it is holding. You'll need to get to it from the top of the duct.
Once the second screw is removed, dislodge the component, but don't remove it since there is a metal tube connecting it elsewhere. There should be enough room to unscrew and wiggle the final stage resistor out and disconnect it. Be careful not to break the free hanging component (I wish I knew what it was!). Replace it with the new resistor and test the climate control before re assembly.
Reassembly can be a little tricky since some of the screws are in tight spots. I was lucky enough not to lose any in the console by magnetizing the screwdriver. I was careful, took my time on every step and spent about 2 hours beginning to end. Not bad for the savings!
Hope this helps!