Cold Temperature Problems?

:banghead: I left for work one night after leaving my 2001 GT automatic outside for about 5 hours. The parking lot is a little raised in some areas where I parked ( ironic however that its a new lot). When i went to work, i used my E-brake to prevent stress on my trans. Well long story short, when i left work I started up the car ( It was a rather rough and buzzy because of the frigid temperatures at night.) and let it warm up for a few minutes, my shifter would not come out of park. the button on the shifter was stuck, and my E-brake felt a little loose. I was able to squeeze the button in after 20 minutes, (knowing i was doing damage) and drive home fine. when i attempted to take my key out, it wouldn't because my shifter was sliding through the gears without the brake.........after about a half hour, i went back outside to take the key out, and it came out perfectly fine............can some please explain what happend, and possibly the damage i did?

cold? might just check the tranny fluid in case, but my mom's old chrysler is impossible to shift out of park when it is cold outside.