Having shown plenty of nerves early on, the Magpies were a team transformed once they went ahead and more performances like this will surely see them rise up the Sky Bet League One table.
The hosts went ahead against the run of play in the 33rd minute when 20-year-old McGregor's low effort from 25 yards found the bottom corner of the net.
The Celtic loanee was to double his tally eight minutes later when Mustapha Dumbuya laid the ball back to him and he passed the ball into the net after taking a touch.
The Magpies ensured the points were in the bag with something to spare in the second half when Crewe goalkeeper Steve Phillips flapped at Jack Grealish's cross in the 66th minute, giving Danny Haynes a tap-in.
An almost-perfect day for Chris Kiwonya's side was crowned with seven minutes left when Canadian striker Marcus Haber rose to meet Greg Tempest's deep cross with a terrific header.