Changing planes from a complex model

I'm not sure if I can do this, so I will ask first. I have parts split from a complex model that have planes I don't like. I want planes in the centers so I have a chance to mate these parts, even though there are no planar surfaces. Can I open the gasket in sketch, and move it so the origin is in the center? If I do that, does it affect anything else?

SolidworksParts And Features