Production programming

For the first time I have to provide firmware for an assembly company to program boards on an assembly line at around 20,000 units a year. I've only ever programmed at low volume which I do manually with PicKit3 and MPLAB. Currently I set the fuses in MPLAB but now I need to have them embedded in the program.

What do I need to provide for them to program the board? What questions should I be asking them?

Thanks.