You can flip the magnet in one of the pickups to change phase. They're not magnetized the way you would expect, with N at one end and S at the other. Instead, they have N along one long edge and S along the other. So, after removing the chrome cover, loosen the screws on the bottom plate that hold the bobbins in place. Don't remove the screws, just loosen them. Then slide the magnet out and flip it over side to side and slide it back in. Remember, one edge is N and the other is S. You want to reverse the bobbins that N and S are under. Tighten the screws, replace the cover and go.
You'll need a monstrous soldering iron and a single edge razor blade (or X-Acto knife) to remove and replace the the cover. If you don't have access to something large enough, then a guitar tech shouldn't charge to much. Especially if you bring them just the pickup.