I am filing my I130 together with the I485, do I only need one G1145, or do I need 2?

Do you mean G-325A? You each need to fill out and sign a G-325A. You will also each need to submit a passport-style photo, proof of the petitioner's citizenship, the marriage certificate (with English translation if necessary), any prior divorce decrees (with English translation if necessary), and (if it is a marriage less then two years) proof of the marriage relationship. Then for the I-485, you will need to submit proof of the applicant's eligibility for the I-485 (copy of visa used to legally enter the U.S., for example), copy of the applicant's birth certificate (with English translation if necessary), two more passport-style photos of the applicant, and the affidavit of support (I-864). If you also want to apply for a work permit, file the I-765 along with another passport-style photo of the applicant. I would recommend consulting with an attorney before filing to ensure that the applicant is eligible for the I-485. If not, then a denied I-485 can lead to removal proceedings.An attorney can also help make sure you are submitting all of the correct documentation to prevent delays in your case.

If you are submitting the applications together, the instructions advise you to submit one G-1145 clipped to the top of the whole package. Hope this helps.