You would file an N-400 if you've had a green card 5 years, or 3 years if based on marriage. Assuming you've reached the 5 year mark anyway, you can file an N-400 90 days before the 5 year mark.
I'm not sure why your N-400 would process any more quickly just because you married a USC in the process. I couldn't imagine it taking a year or more.
I attached a guide to naturalization for the N-400.
Also, I attached a link to find the processing time by specifying your field office location.
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