2003 pontiac aztek key wont turn off

The car turns on and off just fine, the key will not turn to the off position. I was told it was possibly the neutral safety switch. can’t afford to pay the dealer to fix it. what could it be and can I fix it myself?

The neutral safety switch prevents the starter from cranking. The ignition key has to be in P or N.
The shift/steering inter-lock is probably preventing the key from going to OFF. A bad ignition key, or lock, could cause it, also. Look in the repair manual under “steering interlock”.