First, bleed off the fuel pressure by depressing the schraeder valve at the fuel port by the pressure regulator, that way you won't get fuel sprayed in your eyes. Next use 2 correct wrenches so you don't round off the fuel line nuts. One wrench on the filter and the 5/8" on the fuel line nut next to it. If the steel line starts to twist and kink when you turn the nut, STOP, go back. Sometimes, rust and corrosion can fuse them together. Use penetrating oil, lots of it, and let it soak. It sometimes helps to actually tighten the stubborn nut a little to break the adhesion, then try to loosen. If they are still stuck, DO NOT get the torch out. I've actually seen it done. If you can't get it off, pay a professional and I don't mean Joey at the Qwik Lube.
Once off, pour the remaining contents in a cup or glass and look at it. particles and dirty looking gas means it's been awhile. I hope it's nothing but clean gas. Next, try to blow thru the filter. Blow thru the new one first, no restriction. If you can't blow thru the old one, just think how hard your fuel pump has been working just to get fuel up to engine. Do it once, it's easier after that. Change AT LEAST once a year. Good luck.