Towing Issues: Toyota Ignition key failure, routine oil changes, toyota corolla

Question
I'm setting in the Kroger parking lot in SE Ohio at 1 a.m. as they close because my ignition key suddenly won't turn.

Flipping the double edged key does no good.  I've double checked the car is in Park, and my foot is on the break pedal as I attempt to turn the key.  I've even tried to jiggle the steeringwheel, as occassionally, this has prevented the key from turning slightly in the past, but was easily resolved.

I've gotten a taxi home, and discovered a spare key keep virgin at home, WILL turn the ignition and start the car.

What must I do, besides having a new spare cut from this virgin key?  Should I replace the ignition switch?  How expensive is this likely to be?  I've already removed all the excess junk and weight from my keyring, but it may be too late.

Any advice?  Cost estimates?  The car is a 1995 Toyota Corolla with 176,000 miles. We've replaced the tires, the gas tank, a new starter, an alternator, and regular routine oil changes with filters every 3,000 miles, but it still uses a quart of oil every other tankful.
Thanks.

Answer
It sounds like the tumblers inside the lock are going bad and as such they are not totally moving to the proper place with the worn key.

And yes all the "JUNK" on key rings can also kill the lock with the weight being applied in the wrong places.

Now the new key most likely is what you will need to have a copy made from. But then again you might need to get a new lock assembly soon before it totally dies.

As to cost, I really do not get into repairs so I do not have any cost.