Wilbraham brilliantly broke the deadlock in the sixth minute when he controlled Lewis Gobern's cross and swivelled to smash an angled volley high into the net.
Gobern had a shot cleared off the line by Paul Rodgers before Baldock's brace put the hosts 3-0 up. Baldock raced clear onto Luke Howell's long ball in the 16th minute to confidently slot past Chris Dunn and then completed his brace from the penalty spot in the 27th minute.
Baldock picked himself up to score after he had been clattered in the box by Dunn - whose collision with Patrick Kanyuka in the incident forced the Cobblers' debutant off on a stretcher.
Northampton finally showed some spirit after the break and Guinan headed in Luke Guttridge's free-kick in the 51st minute but it proved to be only a consolation goal.