Richard: I am not sure on the Q grill valves as I have never removed one to clean it either. Someone on the list might. However, if you find you cannot disassemble and fix them, I suggest you start looking for someone selling a Q3xx for a reasonable price where you can just grab the valves off it. It is probably going to get pretty expensive to buy new ones.
One other thing to consider is that since you have a Q3200, I am guessing it is not all that old. Maybe a call into Weber C/S will net you some good news. It may still be under warranty.