The Duramax does NOT have a fuel pump to move the fuel from the tank to the engine-! It uses the Injection Pump [CP3] to draw the fuel.
If you change the filter, and try to start it without first priming the system, it will take a LONG time to get it started. There is lots of air in the lines and that has to be pushed out before the fuel can get to the injectors.
On the top of the filter is a large Primer button, and a black screw next to the primer button. Open the screw and pump the primer until fuel comes out. Close the screw-[careful it is plastic] pump the primer until firm, crank engine for a few seconds, pump the primer again-crank a few seconds.
I recommend you rebuild the filter housing with a seal kit from one of the Forum Supporting vendors listed at the bottom. Easy 15 minute job.
Check your fuses under the hood and make sure nothing shorted out. Besides that, have you gotten any codes from this? There is another way to see if fuel is getting to the rail, and purge the air. On the common rail there are the hard lines that go to the injectors. Crack the line lose from the rail using a 19mm wrench. If youve got fuel there it will be 4-5k psi so dont take the line off, just crack it to test. Have someone turn the motor over for a second and see if straight fuel sprays out. If so youve got plenty of fuel and need to look for the problem elsewere. If air comes out with the fuel then you need to purge it all out and it should fire.
Probably not the issue but I think WIF should be 1/4 turn past hand tight. Most likely you need what is said in last sentence of post #3. Or at least that will be needed eventually and is cheap and easy.
You clearly have fuel starvation. Pump the crap out of it, crack the bleed screw, pump the crap out of it, crack the bleed screw, repeat until your arm falls off. BTW if your primer isnt getting hard you are getting air. FIND where you are getting the air.