This one is easy. There really is no 'check', you simply replace it when it is due.
The fuel filter is screwed directly into the inlet of the fuel pump, which is located under the genset base, at the front left corner.
Remove the fuel line from the filter, unscrews the filter from the pump with a 9/16" wrench, and screw the new filter in. Reattach the fuel line and you are done. 5 Minutes max.