Brand new bike? Why mess with it yourself? You paid for a fully assembled bike that should be in proper working order. If you cannot lift the rear wheel with the front brake using moderate hand effort something is wrong and you should take the bike back and have the shop look at it. Maybe they screwed up the cables, specifically where the housing enters the brake lever. On aero levers if the housing is not completely seated (it can be tricky) braking will be mushy and weak. If this is the case the bar tape needs to be taken off and re-done. I would let the shop do this work.
While I agree that V-brakes give more stopping power with less hand effort, I can lift the rear wheel of my old junker with super long reach Mafac centerpulls. You should have no trouble with new properly setup cantis.