I cannot advise you if you should or should not have the surgery. You will have to weigh the advantages, disadvantages, and alternatives with your doctor. However, I will try to address some of your questions.
Regarding anatomy, the gallbladder is located in the right upper quadrant of your abdomen. Bile is ejected from the gallbladder, passed through ducts, and enters the small intestine. Please refer to the following illustration from WebMD:
The most common initial symptom of gallstones is biliary colic, which refers to intermittent attacks of pain, typically in the right upper abdomen just under the lower ribs. You may also feel nausea and vomiting, as well as pain in the right shoulder or back. This is usually happens when the gallbladder contracts in response to a fatty meal. Complications of gallstones include acute or chronic cholecystitis (inflammation of the gallbladder) or choledocholithiasis (when stone leaves gallbladder and gets stuck in common bile duct connecting gallbladder to small intestine).
You had mentioned your prior ultrasound showed dilated bile ducts. This may reflect normal variation, but can also be caused by stones, stricture, tumor, or other process obstructing the common bile duct. This can be further worked up with MRCP (noninvasive imaging test) and/or ERCP (invasive procedure involving flexible tube).