General Eisenhower's farm is part of the Gettysburg national park. It is available for tour through the NPS via bus from the museum. Really a nice tour. It is kinda behind Pickets charge below Longstreet observation tower. He even had Khruschev visit him there, and take a tour of the battlefield. JFK toured the battlefield too.
General Eisenhower had an office on the second floor of the post office in downtown Gettysburg.