Greetings,
Good luck and congratulations on a good choice. I am an ol' retired f00rt myself (Army tho). Take courses when you can, most ships offer internet courses and what else ya gonna do while at sea - ain't like it's a cruise ship!
I made the mistake of listening to my peers about wanting a commission and didn't go to West Point Prep School. Don't listen to them. Follow your dream and don't let them talk you out of it. (For the record, I did get the commission later, once I smartened up!)
The service is a great life, the rules are easy. 1) Do what your boss wants and 2) Do it when you're told. Assuming it is legal, moral and ethical of course.
Have fun and good luck
Regards,