Hi Stephanie,
As far as your pendant goes, US$ 250 for a 10mm Tahitian and a diamond chip is a good deal in bricks-and-mortar world but you can do better online (
http://www.pearlparadise.com/detail.aspx?ID=190 ).
The GIA is not actually a university or any other kind of academic institution. I am not quite sure what it is really good for, but whatever it is it does not include protecting consumer interests in pearl purchases. Having said that, the GIA will give you a pretty certificate to hang on your wall and impress customers with when you have your own bricks-and-mortar store. It is unlikely to help you get a job in a jeweler's store but it does come with a presumption that in the future you will know what you are talking about or at least where to look up the answers first.
Zeide