Spark Plugs and Fuel Pump Relay Switch

Hi I own a 2002 Chevrolet Venture. The mileage on the vehicle is 82000 and the engine size is 3.4L 6 cylinder.
I am having trouble starting the vehicle. Battery works fine. I checked all the fuses and the fuel pump fuse burn't out. I switched that with a new one. The car tries to catch but it seems like the gas isn't getting through.
Should I try changing the spark plugs? How can I reach the back spark plugs? I haven't changed them for about 6 months. I usually do it every 6 months because the mechanic says so.
I am not sure of where the fuel pump relay switch is located. Can you tell me it's location? What should I do with that? I was also thinking about changing the fuel pump and filter while I am at it.
I surely don't want to take it to a garage because I am on a different island and not sure of how much it will cost. I already called around for diagnostic checks and it is $95 an hour. I can't deal with that. I'd rather do it myself. I am a woman and I do know some auto repair mechanic.
It would be greatly appreciated if you could help me out. Thank you very much.