but it is still stuck on an endless sound loop - still playing the gun sound.
There is a fix for the sound problem (not just the one I copied from your post, but all of them). Submit a ticket and you will be able to get the fix for that.

Panel comes up blank. I pressed Shift+1 to bring up main panel, shift+2 to bring up HUD gauge, and shift+3 to bring up HUD background. I clicked the Master on the panel.
Do a complete uninstall and registry clean (remove the CS Weapon entry from the windows registry). See KB #685 for details.

If you still having the missing panels issue - A further problem that can occur is that the downloaded installer is faulty. Click on the link in the email to re-download the file and install it with the new installer.

Is there any way to get a refund? Apparently, there's no support and no documentation.
You can get the manuals from here: http://www.captainsim.com/products/w001/manuals.html

I didn't know I was paying $22 to be a Beta tester.
It works perfectly for me (it always has) and many others. I have never had any of the problems that you are having.

Hope this helps.

Mark