I have been trying to track down all the papers needed for my citizenship application. I am applying and collecting things all the way up to my great grandfather, who was from Sicilia. Any questions these answers will be much appreciated!

-Naturalization Record of my GGF: He was naturalized but I can't understand whether it was a federal, state or city naturalization and therefore I haven"t been able to request it. I DO have a photocopy of it and therefore know the number and everything! That seems promising but still I know that I need a certified and apostilled copy. I wish they would just accept the photocopy that I have and could match that somehow and apostille it!
-GGF and GGM's Marriage certificate: I know that they were married in NYC but no idea where I could request for their marriage certificate. Have tried searching to no avail.
-GF and GM's birth certificates: They were born in NYC. I have my GF's original birth certificate and just need to get it apostilled. I was told that just an apostilled copy of my GM's birth certificate should be enough. I do have a paper about her birth that shows her birthdate and stuff, so that is helpful. I am just wondering where in NYC I could request her birth certificate stuff? The NYC county office?
-GF and GM's wedding certificate. Again, where could I get this apostilled? The county of NY?
-Lastly, I need to get my GGM's birth certificate from Sicilia. I already went to get my GGF's, back when I didnt know that the GGM's would also be needed. Do you know of any website links to get this from or do I need to go back to Italy? I saw one website but couldn't tell if it was legit!
Here it is:
https://www.visureinrete.it/anagrafe/an ... ?Id=082045
THANK YOU THANK YOU THANK YOU in advance if anyone knows any answers to these questions, I greatly appreciate the help! I can see why people pay for this to be done for them as this search is EXHAUSTING! grazie ancora!