if you right click your sketch in your fmt, and choose the little plane symbol and click again you can delete the front plane and select the right plane.
I will clarify this for the benefit of those following.
If an existing Fully Defined sketch is in the wrong plane, then:- Exit sketch FM>RC on sketch>LC on edit sketch plane, PM pops up FM>LC on required plane, PM changes PM>OK FM>LC on required plane>LC normal to
HELP. The property of sketch entity get confusing when you change plane. The previously vertical lines will still be called vertical eventhough it was horizontally drawn. The coordinates of points get confusing too. Negative can be postive and vice versa.
if you right click your sketch in your fmt, and choose the little plane symbol and click again you can delete the front plane and select the right plane.