Depends. Usually low or dirty fluid. Get it checked by a professional.
You would have to replace the whole thing, it only about $30 its a locking pin that looks like a staple pull it out and it should come off....... easy do it your self
In order of probability: Low or incorrect fluid, over-revving engine while shifting, valve body issues (including solenoid failures)
A 1992 Oldsmobile may not shift out of park because the transmission is stuck. Check to transmission fluid to ensure it is at the proper level.
If your Oldsmobile Alero will not shift into overdrive, the transmission may have froze up. Check the fluid levels to determine if you are low on fluid.
Are you talking about the button that will put the shifter into drive, park, etc? If so, I once lost a "U" shaped clip that holds the whole shifter together. I could not shift because the buttons were not aligned. Try pushing down on the shift knob or pulling up on it....if it has a lot of play or comes off, replace the u clip.
Just remove the console and you can get to it.
gear shiftner will not move out of park
Shift cable
If you are parked on a steep hill or the front wheels are parked hard up against a curb it may cause that to happen. It may take some force to get it out of park. If that fails to work, check for a blown fuse.
To remove the shift knob on the 1999 Olds Intrigue look for the pin that is holding the knob in place. Remove the pin and pull up on the knob, replace kob and pin.
The 2000 Oldsmobile Alero shift solenoid is located on the top of the transmission. The shift solenoid can be access by removing the inside shifter console.
There is a staple on the front of the gearshift just below the knob, remove it and lift the shift knob.