I took my 2008 Volvo XC90 into a shop yesterday because the check engine light was on. They diagnosed the problem as the fuel pressure sensor. They replaced the sensor and did an oil change. When I picked up the car, the gear shifter wasn't shifting easily and when I got it to the Drive position, it would immediately slip out into manual - I noticed it right away and never even made it out of the parking lot. The same mechanic just called me and said that it was a giant coincidence, but the gear assembly needs to be replaced (transmission is fine). I don't want to be charged for the work if it was something that they messed up. The timing is rather suspect. Does anyone know if there is any way they could have jacked up the gear shift in the process of diagnosing/fixing the fuel pressure sensor and the oil change? It shifted very smoothly before I took it in and it never had problems with slipping out of gear before.

Thank you in advance!