Can a Valve-body failure prevent the vehicle from going in to gear.

I have a 2002 Saturn SL2 the car
won’t go into any gear. Changed the
valve body 2 years ago and before it
stop moving on it’s on the gears start
slipping again. When the car broke
down there was a high pitch sound  
and burnt transmission oil smell. I
checked the oil from the dipstick it
looks and smells fine. The vehicle
operates in park normally and the
engine sound changes like normal
when you put in gear. The vehicle will
not move on it’s own but if you push it
while it’s in gear the vehicle seems to
move on it’s own somewhat making it
easier to push. I am not sure of what I
should replace.