Lincoln grill. It's next to the old depot. Excellent breakfasts at good prices.
Go to Devil's Den and Little Round Top. I reennact there almost every year and usually get killed by the second day...
Forget the 'ghost tours' and such, theiy are ok but just walking around will give you a feel for the place. If you want to get creeped out visit Antitiam and walk the sunken road. If you don't feel something there then you may be dead yourself.
I'll second the Lincoln Grill. Nice atmosphere, too.
Assuming you've boned up on the battle as much as possible, the only other thing I'd recommend is going out to The Angle in time to watch the sunrise, or at least before the crowds get there. The silence is deafening.
I am a Rev-war reenactor. We share a common place at Endview Plantation in Newport News. That was a Rev-war hospital and a Civil War hospital. That place is haunted!