Restoration or refinishing most old furniture will increase the value. Face it, much of our old furniture comes to us in bad shape and could use a refresh. Ordinary, low market, or previously damaged furniture benefits from a face lift. The loss in value comes when the furniture is very old, of high quality with a unique finish or patina; when the furniture was made by a well known craftsman (think Gustav Stickley), or if it is a museum quality piece.
A badly damaged piece will not hold value so restoration or a refinishing will make it more attractive so more desirable.
Before you opt for a professional appraisal, do some research on your own. Learn the age and quality of your wood furniture. Find out what similar pieces are fetching in the market. Make sure that the cost of a professional appraisal will be worth it.