Remember it's your body and your doctor works for you, not the other way around. If you feel uncomfortable with surgery then your doctor should not try to unduly persuade you (unless of course it's truly life-threatening). It's your choice, not theirs. That goes for any surgery, not just gallbladder.
Keep hunting down specific information on the impacted stones. Try one of the other forums if no answer on this one. Someone out there must have an answer to this.