It could also be the lock cylinder. Typically though when it goes bad it just locks up and it's done. I would have the shop check the shifter linkage. You could also do it yourself. You will need an 8mm or 10mm socket. Put it in park and open the hood, take out the airbox and you will see the shifter cable. Loosen the bolt and and move it a little bit and then let it set itself. Tighten and check.
