MARTA does not have a rail station directly serving Amtrak, but the route 110 MARTA bus calls there. It will take you to the nearby Arts Center station from which you can transfer to a direct train to Atlanta Airport.
It's located on the airport near baggage claim. Can't miss it.
Yes. Not sure where you are located. Are you a visitor to the city? Every hotel have free maps, brochures listing all MARTA stations and their locations. Ask any bellman.
Thanks! Your answer is awaiting moderation.