Jun,
You do not have to restart the whole model if you just updated the wing. All the models are modular. If you only updated the wing, you can keep everything else the same. In the assembly file, make sure you attach the updated wing to the fuselage. It should fit as long as you kept the chord length the same.
You are strongly encouraged to create your own CREO models from scratch. As long as you show the wing, fuselage, empennage, landing gear and payload, you should be all set. For sizing, make sure your wing is large enough to generate enough lift to be able to carry the payload you have selected.
Thanks
-Dr. Khalid