How can i take appart a bmx pedal?

I bought a new rear wheel for my bmx bike and the driver is on the left side. I switched the cranks the opposite way.now my problem is that my pedals are backwards now.the "L" pedal is on the right and the "R" pedal is on the left.if I put the whole pedal the correct side,it would mess up the crank thread.can someone tell me how to take it appart to switch only the plastic part?