There is no such thing as an "established" or "official" domain appraiser anywhere, and anyone who sells you an appraisal is really only benefitting themselves, not you. I'd stay away. They can actually do more harm than good by selling you an appraisal that drastically overstates your domain's value, just to make you happy with their service in the hopes you will buy more.
You can get a good grasp of market values by browsing through the sales and appraisal threads on this site - that will be the highest quality and cheapest lesson you will ever learn on the topic.
Best of luck, and welcome to DNF!