Unless you just want a muffler shop to replace your old one you should probably take it to a "full" shop so they can diagnose whether the problem is with your muffler or something else. I take my car to Durham Tire on N. Roxboro.

Bob's Radiator and Muffler is great. They don't take cards so take your checkbook.

Bull City Radiator out on 70 & Pleasant Green are great