However, City allowed the visitors to equalise minutes before half time. City failed to regroup after half-clearing a corner, and Barry Conlon beat Alan Fettis from six yards out.
But City took a foothold on the game after the break, scoring two goals in quick succession. Debutant Jason Price put City 2-1 up by following in a deflected Stuart Elliott shot.
Then fellow debutant Alton Thewell gave City a 3-1 lead with a superb half-volley from the corner of the penalty area.
Collett then caught a Stuart Elliott header to deny him his first of the season.
Danny Allsopp and Jason Price both had efforts well saved by the Darlington keeper, but a fourth duly came 8 minutes from time courtesy of Allsopp, who lashed a shot into the top corner after getting in behind the defence.
14,675 were at the KC Stadium to see City go top of the league for the first time since the opening day of the 2001/02 campaign when Brian Little managed his side to a 3-1 win at Exeter. Before that, the last time City were top of Division 3 was in 1996, when Duane Darby opened the season with a hat-trick in the 3-2 win against today's losers Darlington.
City line-up (4-4-2): Fettis; Thelwell, Hinds (Whittle 54), Joseph, Delaney; Price, Green, Ashbee, Elliott (Keates 80); Burgess, Allsopp (Forrester 83).
Un-used subs: Musselwhite, Appleby.