Gear shift sensor?

My sister has a 2006 HHR which seems to be having some transmssion/gear box issues. She took it to a local shop who did a diagnostic and told her that a sensor was going bad that delt with her gear shift. The HHR is a automatic but when she puts the car in park sometimes the doors don’t automaically unlock like they are suppose to and she has some difficulty with putting it in park some times or getting it out. Also when driving she says it seems like there are problems with the transimission finding the right gear. The place she took it said the sensor was about $90 and it was a 3 hour job in replacing it. However said she could not do any damage by driving it till she had the monies to get it fixed. Does this make any sense?

I can understand not getting a stick out of P but are you saying she has a hard time getting it into park and other gears?
There’s a fair bit of mechanical resistance getting it into P and other gears, then? If so, it is probably some sort of linkage problem.