what patty579 and ari4u said is true. marrying a USC will pardon your overstaying. however, don't travel outside the US while waiting for your GC because it will trigger the 3/10 year ban, regardless if your spouse is a USC. pardoning ones overstay due to marriage to a USC means that you do not have to go back to your home country while waiting for the application to go through. that you can stay here and even work legally (if you apply EAD) while waiting to adjust your status. but once you leave the US before you receive your GC, you will trigger the 3/10 year ban since you overstayed.
now, i have a question of my own. i know out of status/overstaying is somewhat different if you have an F-1 visa because they are looking at one's d/s (duration of status). is it true that if you have an F-1 visa which is still valid (meaning not expired) but you fell out of status (meaning did not enroll full-time or failed to enroll a semester or two), and you married a USC, you can still apply for an AP (advance parole) and leave US for a vacation while waiting for your GC. meaning, you will not trigger the 3/10 year ban because technically, your F-1 is still valid through the D/S (duration of status), you just fell out of status. is my understanding correct?