Rare hand painted porcelain with gold vase. How to clean it?

Grandma had this little goody carelessly tucked away in an over-crowded china cabinet where something was spilled long, long ago and many pieces need a good cleaning. There is one piece in particular, after some research, that is fairly valuable and rare. It is over 100 years old, completely hand painted, and trimmed richly in gold on the handles and rim. It has gunk all over it and even inside I can see where someone must have put a plant, with dirt and all. This needs a good, non-damaging, cleaning treatment. I'm not sure how to go about this with the paint and gold. I'm just a little worried some of it might come off with the wrong cleaners & methods.