Forget about start to finish; id be happy just to see proof of concept source (like 360's checksum code). The rest wiill just take some long term tweaking.

FTDI have some code examples on their website, one specifically shows how to open a port & set baud / comms parameters. Handling the 9 bit transfers looks ok too, with 8 data + 1 parity bit. Change the odd / even parity parameter to set the parity bit 0 or 1 depending on the transmitted byte, and you will end up with 9 bits to sent. Receives can be handled by inspection of the parity error bit from the driver & some logic to set the 9th bit appropriately. I cant think of any other way to do this.

I'll try to have a play when i get some time....