In the military discipline is forced. If one has not the intention to find that same discipline within oneself then this is, perhaps, the worst way to achieve it for within the armed forces you are not encouraged, it is a simple matter of obedience being enforced. There are much better ways to acquire that regimentation that do not require such a considerable sacrifice and/or investment. That said...
The Armed Forces, at least in Canada, provide unparalleled income possibilities, opportunities for advancement and recruitment bonuses. They will pay your way through 'school' and not just what they select for you, but allowing you the freedom to direct your own course. Now, admittedly, this is due to the fact that in Canada enlistment is at an all time low, such that we as a nation are hard-pressed to meet our requirements to the UN abroad... or even for ourselves at home. This is not the case in the United States of America; with a fighting force of such staggering numbers, as I understand it, enlisting in the reg forces is second only to slavery although, this is not first hand knowledge but rather stories I've heard from others serving.
A good person to chat with would be Hyfe, even though he is a submariner and not a Marine. He could give you a better idea of the reality of joining the armed forces. Also, Telan would be a good person to speak to on the subject even if the majority of his experience is European.
And remember the history of the Marines... and ask yourself if that is a tradition you really want to associate yourself with? Remember the Airborne Rangers? The Green Berets?
All I am saying, or anyone else for that matter, is exersize your most critical of thinking when debating the issue of such a heavy commitment.
If it is a choice you chose to make; you can be assured that we, at least I, will support your freedom to select your own path.