A little further down the road in Nanticoke on MD-349 is
Roaring Point Waterfront Campground. You might want to check that one out too. I camped there once but it was back in 2002. I'm sure things have changed since then. At that time, most of the FHU sites were occupied by the seasonals and I was only able to get a W-E site. However, they do have a dump station.
For a sizable grocery store (Food Lion), it's located right on MD-349 at Salisbury. At the first traffic light after passing the Food Lion is a Rite-Aid and a McDonald's.
The major shopping area (Salisbury Mall, "big box" stores, dining, etc.) is on US-13 north. You can reach US-13 north by either taking business US-50 east (through town) or taking business US-50 west to Naylor Mill Rd. Turn right on Naylor Mill and follow it to the entrance ramp for US-50 east (Salisbury Bypass) Then take the exit for US-13 north.
I was just in the Salisbury area last weekend, but not camping.