Forgot to mention the blower motor resistor. If the blower motor stops working on level 5 but works on everything else, it's the resistor. Or if it doesn't work at all. Quick and easy fix under the pass side of the dash.
Also another thought. There are 2 different climate control systems for '03-07, the manual "slider" style:
You must be registered for see images attach
And the digital style:
You must be registered for see images attach
NOTHING INTERCHANGES. THEY ARE 100% DIFFERENT SYSTEMS. The manual slider is pretty reliable. The digital is hit or miss, I've had both in low and high mileage trucks. The digital, the temp control knobs will get to where they won't really adjust the temp. You'll spin them and it'll stay the same or barely move, you have to spin the VERY slowly to get the temp to change. Usually, you can pop the knobs off and spray some electrical cleaner in there, let it dry and put them back on and be ok. Also, the display will die sometimes or some of the buttons will quit working or the whole head unit will die. You'll have to replace the headunit at that point. YOU CANNOT CONVERT TO MANUAL/SLIDER. As I said, the whole system's different. Head unit/ducting/blend doors/harness/all of it from my research.
The manual is much more reliable. It can also die and you'll have to replace the headunit but they last alot longer. The LEDs will die in all of them (and the steering wheel controls, and the door switches, and the gauges lol) but they'll prob still be functional. My current '05 has the slider style and other than some LEDs being dead it works great.