Tuan, none of the Extreme APs are designed to be user-serviceable.
If the AP is out of warranty and you do not have support on it and don't plan on it in the future, then you can attempt something like this at your own risk.
As far as the radio cards, they are both dual-band cards. This is why they both have the same part number. They are interchangeable. If you can locate a replacement card somewhere, it should work.