Water is spewing out of the air vent on the back my washer

I really need more information here. Are you saying that there is water spewing out as soon as the fill starts, or does the machine fill and fill and fill until it finally comes out of the vent.

If the latter is the case, then this is almost certainly a faulty pressure switch. It may need replacing or it may have just come loose in the machine and be hanging in a position that causes it not to work (I only saw this happen once, but in my own machine as it happens!). To investigate, you will need to take the top off the machine (My article http://www.fixya.com/support/t1543617-door_seal will explain this). and then take a look at the switch.

You are looking for a circular device, a little smaller than the palm of your hand with 2 electrical wires and a plastic tube about the thickness of a pencil attached to it.
The way this thing works is that as the water in the machine fills up, it pushes a little water up the tube and the pressure of the water compresses air in the tube which operates a tiny bellows device in the unit, switching a microswitch in it and cutting power to the taps that let the water in.

You MAY be able to fix it without replacing it. with the machine empty and unplugged from the mains, remove the tube and blow down it to clear any water in the tube out (If more water that there should be got into the tube, the air pressure as it fills will be too low and the cutoff won't work, blowing down the tube clears out the water and the switch may now work properly again when the tube is replaced.

If this fails, then you will need to replace the switch. Anyone who deals in washing machine parts will be able to source one for you. The goos news is they are fairly cheap.