You became a permanent legal resident on December 4th, which means you are eligible 90 days prior to Dec 4th of 2012. Yes, it is 90 days before your 3rd year LPR anniversary and not marriage.
Biometrics - some people do not get another notice when applying for naturalization if they have taken ones within 12 months, but others have said that they had to go anyway.
Read the naturalization guide - very very helpful and has all the information you need. http://www.uscis.gov...ticle/M-476.pdf
