Ignition Cylinder wont turn?

Hello, My 2000 Mustang GT ignition key suddenly doesn't turn. I can't figure it out. Its not like it started to get stiff, like the key was being worn over time, its just one time the key seemed like it was the wrong key. The key is an Access replacement key. It had been working fine and it still opens all the doors, trunk etc. I had heard (read) someone said something about a park relay? Anybody know of this? It is an automatic. I have tried all the jiggling of the key, steering wheel, pressure on the brake etc.

Any suggestions would be of great help. Can I replace the ignition cylinder without having a working key to move it into the run position? Can I service this without deploying the AirBag!

I'm a handy guy, an aircraft mechanic and an ROV pilot /technician/ submersible engineer... I have a good compliment of tools and equipment and can borrow anything else I may need.

You help is greatly appreciated and thank you for your anticipated assistance,