I am trying to complete a 30K maintenance and have not been able to
locate the gas filter. I have not been able to spot it in the engine compartment or anywhere under the car. My next step is to get the car
up in the air and look harder but any tips would be appreciated for locating
it and changing it without too much spillage.

I'm not sure on the Legacy but you could look at the gas tank where the fuel lines come out, it's become common practice to locate the fuel filter there.