I have a 2003 Envoy and when it's cold out and I start the vehicle the gear shift locks up and prevents me from driving off, sometimes I’m waiting up to 30 minutes for the shift to unlock. Also when I drive off somewhere and I put in park, the button on the gear shift doesn’t release preventing me from turning off the Envoy completely. I have to sit there until it unlocks so I can retrieve my key from the ignition. I imagine a brake type cable in the gear shift that may need to be changed out, but I am unsure. I'm trying to prevent being ripped off again by a mechanic claiming I need something done when I don't. Can anybody help me out on how to fix this? Thanks.