For a certified copy of your marriage certificate, contact the vital records office in the state where you were married for instructions on how to request a copy and information on any fees. Even though the guidelines vary by state, all requests should include: Full names of both spouses at time of marriage.
Yes, you may check-in for your United Airlines (UA) flight at the airport ticket counter from 30 minutes to 3 hours before the scheduled departure time (depending on your departure city and destination) and receive a printed boarding pass.
How far in advance you need to check in depends on what ticket you have. If in doubt, arrive with time to spare and have a croissant. Due to increased passport controls give yourself at least 45 minutes at busy times such as weekends and bank holidays.