Get a rental car.
You’ll want to take a bus tour of the battlefield, but you’ll probably want to drive it yourself also, and stay longer in some areas than the bus tour will. Also, you may want to see some of the other local historic sites that aren’t necessarily covered by the tour.
I don’t know where to stay anymore. Been too long since I was there. We were there four days the first time and could have stayed a little longer. But if you don’t have a way to get around you won’t need to be there that long.
Try the Farnsworth House BxB in Gettysburg, historic, haunted and they have a great story telling program. There is also a hotel there of note.