Your consulate here in the U.S. will renew your passport as long as you are in legal status. I suggest you get that done right away.
When you marry a USC and adjust through your spouse any overstay is forgiven. Before you overstay make sure your plans are sure as your status will be affected by the overstay if you do not adjust through your spouse.
It doesn't matter if your passport has expired. You can still get a green card through marriage.
(213) 394-4554 x0 Mr. Shusterman is a former INS Trial Attorney (1976-82) with over 35 years of immigration experience. His response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
I answered this question for you in your other post.
NYC EXPERIENCED IMMIGRATION ATTORNEYS www.myattorneyusa.com; email: firstname.lastname@example.org; Phone: (866) 456-8654; Fax: 212-964-0440; Cell: 212-202-0325. The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter.