Ge Dishwasher water valve ??

I have a GE dishwasher that is not cleaning properly. A friend said it is probably a faulty water valve. I checked the float and it appears ok however, when running a cycle the basin only has one inch of water in the bottom. Is this enough and how does one go about changing the water inlet valve ? Is it difficult ?
Any help would be greatly appreciated.

Thank You

Mike V.