Brakes locking up?

Hello. A few months back I had topped off the brake fluid on my 2000 Ford Taurus with 115k miles with power steering fluid by mistake. My mechanic flushed the brake system and replaced the rear brake mechanism because there was a leak in the rear brakes. He also mentioned that I need to replace my front rotors and pads.

For a couple of months now I am experiencing a shake in the steering wheel when I stop at speeds, recently I am experiencing that my braking system is sticking. When I release the brakes, the car does not move and I have to accelerate to maintain speed. Also, when I drive more than 10 minutes the brake pedal becomes hard and at speeds above 40 mph the steering starts to shake (as if overcoming the resistance of the brakes.)

Do I need to replace front rotors, pads and the master cylinder or is there more in the braking system that has gone bad? What else should I check in the braking system? Thanks!