Would someone know where the file is located where the game gets the guest and animal names from. This might be taking customization a bit far but I’d like to delete some of the choices the game makes, and perhaps input some names myself.

The game randomly generates peeps and their names, so it doesn't need any files for them all. That would be a waste of hard drive space. But if you make a peep, it is specifically designed by you and it has to be the same all the time, so it makes a file for all the peeps you make in Program Files/Atari/RCT3/Peeps.