I haven't seen more of Hagerstown than the gas stations and outlet malls. I'm not sure much interesting is there, but feel free to prove me wrong. You're quite a ways from the water in Hagerstown, so I'm not sure how much local seafood you're going to get.
I'd suggest driving over to Frederick, MD, which is a charming town with loads of antique stores. Brian Voltaggio (of Top Chef fame) has (had?) a restaurant there, Volt. IIRC, there are many acceptable dining options, including a passable Spanish spot, if it's still there.
Berkeley Springs, WV, in the other direction, is also lovely and much smaller than Frederick. It's more of a resort town. I spent a relaxing long weekend there years ago, and recall eating well.
Safe travels,
Ronna