Congrats on your awesome road trip! You will have a blast!!
My words of wisdom are... Do you know how to open the fuel door? You unlock the doors and press on the rear most part of the fuel door, it then becomes ajar.
Also... but a liter or two of BMW engine oil. Its not uncommon for our 135i's to use a quart or two of oil on a long road trip. Know that our cars do not have a traditional dip stick... its electronic on the dashboard. You use the board computer to check the oil level. Or the car will tell you when its low.
Perhaps there BMW NA videos might help you out...
http://www.bmwusa.com/Standard/Conte...modelcode=0922
Dack