Is it possible to convert a MacBook Pro from the glossy to the matte option?
Unfortunately, it is completely different type of display. The antiglare is a higher resolution and has different bezel, so it's not possible to upgrade an existing display, short of using a screen film with it. 

You would have to get this done through either an Apple Authorized Service Provider (AASP) or an Apple Store. The Apple Store almost definitely will not put something on the MacBook Pro that it didn't come with, but an AASP might. The only way to find out is to ask!