I had to do the exact same thing. Carefully cut the rudder from around the hinge points leaving a lot of material on the hinge points at first.

Then go back and pick off the glue from the hinge points. Epoxy doesn't stick to the plastic which is why they have barbs.

Then build a new rudder and use the existing hinge points for attachment. I just posted this link in another thread, but it shows exactly what you need to do.

http://www.airfieldmodels.com/inform...ints/index.htm