Marine Infantry? Is it for me?

I am 20 years old, graduated school in 2009 and havent really done much since I graduated. Havent started college yet, and currently do not hold a job... I decided to look into the Armed Forces, going with marines, and now currently DEP'd in, awaiting bootcamp. I feel they have everything I need to have structure and direction in my life. My concern now, is MOS... I am currently listed for mechanics/construction, but Infantry has been stuck in the back of my mind... I want excitement and just that full expierence as a marine. That honor and respect they hold up. And I really would like to pursue it. I just want to know if it is for me... I planned on going into mechanics/construction, and going to school for criminal justice (would like to be an officer of some sort). And thought it would be good to have the skills of mechanics.construction. So my MAIN question here is, how would infantry benefit me in the civilian world? Do I HAVE to stay in infantry? I dont want to be out of (IF I chose to switch out) it at 24-28yrs old with no college education... OR, would infantry help me get to be a successful military/police officer, without college expierence? If anyone with real knowledge of this could help me? It would be greatly appreciated. Thank you!