Flying with baby!

K
So I'll definitely be calling the airline next month for more information, but I thought other mommies with real experiences might also be helpful. I'm a FTM and this November, when my little one is just over 3 months old, I'm going to be flying across the country with him. Alone, to visit my parents/his grandparents. Hubby will not be joining us because of work. It's a 5 hour direct flight. I did not purchase a seat for my baby, so he'll be on my lap the whole time. What do I need to know? What can I/can't I/should I bring on the plane? Any other advice?! I know it's almost 2 months away but I am terrified at the thought of having to do this with no help. I don't even know if they have changing stations in airplane bathrooms? If I'm pumping, am I allowed to bring milk on the plane? (I'm sure that's a question for TSA because of the liquid restrictions). I know I can check the stroller right before boarding the plane - I'm hoping that applies to the whole travel system with his infant car seat, because I'd like that to come with us too? What's the best way to keep him calm during takeoff? We're excited for the trip but flying there and back seems so daunting! TIA!