How do i make sure that a jeweler is telling me the right prize, composition etc of a gold ring i already pos?

actually my boyfriend has gifted me a gold ring but it looks like the gold is quite old ( i mean it isn't having a polished look). i want to know every detail about the ring like how much carat is it made of, what would be its prize, how old has it been made. means every detail. i live in Chandigarh, India. i want to know the current prize of gold in Chandigarh. but i have no knowledge about purchasing jewelry as such. how do i make sure that the jeweler doesn't takes advantage of me being so dumb in case of jewelry. please could somebody help me?