Not sure what you mean by a SEALs contract. If you mean a chance to go to SEAL school, then you should have taken it! If you are into that kind of thing, that is... I'm not sure what part of "how the Navy works" that you disagreed with, but to each his own. The Marine Corps is unique unto itself, but ultimately a department of the Navy. I never wore a Budweiser, but I proudly wore an EGA for years.
Anyway, congrats on the choice, and you'll be fine. I made the same choice in '93 when I stepped onto those little yellow footprints at PI. I went in September and had black flag days, graduated in Dec when it was snowing. Crabs, sand fleas, crazy DIs, crazy recruits, you name it. Just know that everything is a game, and you just have to play along. When you're standing there on line, naked, and holding an M16 out straight by your pinky in the front site assembly, try not to laugh. It'll happen. The FMF was a much different place. Everyone was somewhat normal. My best advice to you - DO NOT GET MARRIED. I saw too many marriages dissolve violently before and after deployments. Lots of women want to marry a Marine, but want someone to keep that bed warm when he's away on deployment. Be careful.
Don't be one of the idiots who gets messed up before he ships out. A few people thought it would be a good idea to get high before MEPS, and ended up pissing hot at boot camp. You're soon to be part of the finest fighting force in the world. Good luck and welcome to the club.
USMC 93-97
0231
Armed Forces Service Medal
NATO Medal
Good Conduct Medal Sea
Service Deployment Meritorious Unit Citation
Navy Achievement Medal
and a few others I can't remember right now...