From the description you give I suspect the water level switch or hose is the problem.
If the washer is overflowing then the first thing to do is turn the timer off or unplug the washer. If water still comes then the valve is the problem.
If the valve will stop filling with the timer off then the problem is with the water level switch, hose or air trap.
What I suggest for this is to empty the washer and then access the water level switch and remove the plastic hose. Check the hose for any kinks or small pin holes. Try to blow through the hose towards the air trap. You should be able to blow without to much effort. You might even hear bubbles from the air trap. If you can't blow through it then the air trap is blocked.
If you can blow through it then hook it back up and try another cycle.
If the air trap and hose are okay and still the water doesn't shut off then most likely the pressure switch is the problem.
Any parts you need can be obtained from the following link:
The images below may be helpful to you.
Remember to unplug the washer first.