Right, well you definitely CAN open up a 2020. Often it involes unscrewing the base and lifting the sleeve off, sometimes there's screws involved but I'd be surprised if you needed more than a small Phillips to get into it.
The diapraghm may have been damaged or the XLR. Is the audio distorted? Is it sensitive to cable movement? Is the pick up pattern still cardiod (move around the mic while speaking and note any level changes). A replacement diapraghm or a damaged solder connection might be the solution, but I recommend contacting AT and finding out if they do mic repair unless you've access to an electronics geek.
The lesson for today is say no to cheap stands, it's penny wise.