I believe devilbones said it best, as far as the Marine Corps lies within your options, that title will come before all else no matter what job you hold.
It's a long road brother and I've seen the best of them fall off, drop pack, quit, etc... and I'm talking all the way from boot camp to ITC. YOU are in complete control of your future, as long as you make the right choices, excel in your MOS to include self education and hard work. That will get you a ticket to the big show one day, and establish a solid foundation required from those who succeed in this community.
But for now, it's the 5m target you need to focus on, which is boot camp if you choose to earn the title Marine. And as far as picking an MOS, you can choose something to challenge yourself that you have no idea what to do or you can go with the polar opposite and something you already enjoy to enhance your skills. Here's the sweet part, it doesn't matter if you're an admin clerk, motor t, air traffic control, or a recon Marine, because it all applies to MARSOC.
Anyways, good luck with whatever you decide.