We actually just had an episode of Behind the Lines the other night on this exact topic! I recommend you check it out, it will probably answer all of your questions and more that you didn't know you had, plus some tips and advice on how to best utilize FIRST Choice:
Behind the Lines S03E05: FIRST Choice and the Virtual Kit with Jerry, Liz, and Kate Pilotte
The episode features Jerry Budd and Liz Smith, AndyMark employees who are involved in running FIRST Choice as well as Kate Pilotte from FIRST who is in charge of pretty much everything related to the Kit of Parts, so this is all straight from the source.