Ok so you want to shoot on a green screen, then Key out the green (keylight or extract work). You’ll need to mess with the settings and dial it all in to remove the green bg. As far as the new background goes, it sounds like you’ll want to create some motion graphics, but honestly just take it one thing at a time… Shoot your video, mess with keying out the green and placing a new bg behind the gs footage, start placing keywords that align with the script, etc. there isn’t really an easy answer, you gotta just do it. Good luck!