The key won't turn in the ignition which appears to be locked

probably need a new ignition lock or your key is wore. ignition locks arn't too bad to change depending on the vehicle.

Usually a sign the tumblers in the lock cylinder have worn out or jammed.
You may have to get the lock cylinder drilled out and replaced.

If the ignition normally only locks with the vehicle in park position, then check the switch on the gear lever mechanism is working.
If not, then you'll have to jiggle and wiggle that key out or replace the ignition lock.

Make sure your steering wheel isn't locked. Sometimes a key won't turn until you jiggle the wheel while trying to turn the key.

If the ignition wont lock in place,just redo it but this time you need to realize that you install the key cylinder with the key in the ON postion,straight into the lock cylinder housing,aligning the retaining tabs,on the key cylinder with the hole in the lock cylinder housing.Then turn the key to the off position,

Not sure what the problem here is.
The codes are for the security system - - the key is not sending a signal or the right signal for the car to start.
Could be a problem with the lock cylinder which may have a sensor for the key inside it.

make sure the stick is in reverse and the key is all the way in the ignition

If your steering wheel is locked, turn it a bit away from the locked position. Key should turn now.

Otherwise, you may need to replace the ignition or you have a bad copy of a key.

Ignition - Key Stuck In Ignition Switch/Won't Turn Bulletin No.: 06-02-35-005 Date: February 28, 2006 TECHNICAL Subject: Key Stuck in Ignition, Key Will Not Return to Off Position, Shifter Button Won't Release in Park Position (Adjust Shifter Detent Finger) Models: 2002-2005 Chevrolet Monte Carlo Condition Customers may comment on any of the following conditions: - The key is stuck in the ignition cylinder. - They cannot return the key to the off position to remove the key. - The shifter button won't release in the park position. Cause This condition may be caused by the detent finger shifting over time. This may result in mis-alignment and binding of the shift rod on the shift position guide.
WHERE YOUR SHIFTER IS YOU WILL HAVE TO TAKE IT APART ..MAYBE THE RUBBER BOOT IS IT THE WAY,OR THE SHIFT LOCK SELINOID WHENT BAD

This happened to to me with my ranger. I went and bought in ignition and a junk yard and no problems after that. That way your not out of a lot of money.