It seems that I accidentally set my CCSM window's transparency to 0. Now I can't see my CCSM because the transparency is 0. How to revert this? thanks
Well don't feel bad you aren't the first one to make that same exact mistake.
The solution from this Webupd8 post is to reset all of Compiz's settings with this command, then log out and back in (or just restart). Read the linked post before you do this, it has several points you should consider.
Be careful with CCSM, it's easy to really mess things up fast when experimenting with it.