What, specifically, are you asking for regarding tuning and strings? For tuning you have to tune yourself. For strings you can travel to one of the harp retailers, but it is easiest to just order on-line.
The closest retailer would be the branch of the Virginia Harp Center that is located near Philadelphia in Haddonfield NJ. Since they sell used harps they can probably give you a rough idea what a harp is worth. However if you are looking for an appraisal for insurance reasons they may not be able to do that, but you can ask. The website is at http://www.vaharpcenter.com/index.php and their phone number and address are located in the Contact Us section on the web site.