Wont change out of park.

I have noticed recently a decrease in performance lately, but never anything the mechanic could diagnose. Then last week I put new tires, flushed the transmission fluid, and aligned it. The following week I was turning a corner and the steering wheel became difficult to turn. I got it home and a few hours later I went to leave in the car when, it started fine but it wouldn't change out of park to drive or any other gear. Today after a little research, I pried the little plastic cap off where the button is to manually switch the car out of park. So the car drives, but very poorly, the steering wheel is still hard to turn, and the air conditioner wont turn on. And no power at all. All these things happened at the exact same time. Plus the car feels like the rear end is "slipping". I take it to a mechanic on Monday but I am traveling and don't want to get "burned" any ideas of the possible cases?