can you feel the wheel turn at all? just a little bit, some times you need to push it hard to one side or the other and then try to turn the key.
ive never had a gp wheel off, but they used to have a slide bolt that went into holes in the wheel and locked it, if the cars wheels were turned or on hill putting pressure on the steering wheel the key would not turn till you turned the wheel off the lock so it would be free to slide back out of the wheel.
are you on flat ground with the wheels straight?
could try to jack the front end up, that may loosen up the lock in the steering wheel.
