If you have tried all other steps to unlock it before (wiggling steering wheel ecc...) I guess you have 2 Options.

1. Removing the pin that not allows the key to go in with the use of a dremel
2. Removing the steering lock housing and unstuck the mechanism that keeps the pin in place.

When going for step one, you still run the risk that the problem is not the tumbler but the steering lock housing.... after having fixed ours, I would say rarely the problem will be just the tumbler when you don't get the key in.