On the bright side, you can reuse the ECU. Just change the coding from auto to manual.
It's been done, you need the pedal assembly, master, slave cylinder, and lines, and transmission. Then cut a hole in the firewall for the master cylinder and done.
I would go for a low mileage used one, it should be cheaper. I would buy a new master and slave. should be able to find pedals online cheaply as well.