Transition Problem in trailblazer plz help me if u can

Hi guys,
I've a 2005 Trailblazer,Auto. Trans., done 51000 Km only, I was driving the car and when i stopped in the parking i moved the gear to (P) and removed the key, i found in the meters board the gear still on (R) position, i tried to move the stick to (P) but i found the stick is already in parking position, i tried to generate the car but it doesn't start , tried to move the gear stick it doesn't move, and i found that the engine oil pressure meter at lowest level, and the checkup engine light is on, and the foot breake is hard like a stone..... i don't know guys please help me if you can