Wow, thanks for all the adivice. I was a little leery of posting, wasn't sure how an ol' worried mom would be welcomed

Couple of things in response to comments made (I saw the ones that were pulled, but can't remember them, sorry):
I only used the word 'underachiever' because I read quite a few threads here and it seems many considered themselves underachievers in high school. Believe me, I know what you mean. It was not meant to be derogatory.
He is joining the Navy because he wants to, not because he has no other option. He has a 2 yr scholarship to the local community college, where he could go until he decided what he wanted to do, and then there is enough $ set aside for 2 yrs to finsih a degree. In fact I told the recruiter that though the educational benefits were nice, and he would most likely take advantage of them, they were not really a part of his decision.
I made the comment about him not minding being a cook because his main motivation is to join the Navy. The nuke thing was presented to him after he made that decision. He essentially is still a kid and hadn't really thought ahead 6-8 yrs. His father and I talked to him and explained why he has to. And why 'we' thought he should work at something where he could contribute his talents. Though he makes a pretty good lasagne LOL. He has thought about this as much as a normal 17 yr old can, but it's true as one poster said, he really doesn't know what he's getting into. He has to rely on what others tell him and then sort through it all. He did sign the papers a couple of days ago, so he is in the nuke program now. Will he succeed? Of course as his parent I hope so. But it seems even if he doesn't, they will retrain him for something else rather than just make him a janitor. However, I am in no way suggesting janitors are not important in the grand scheme of things. every position is part of the team. We just don't want him to waste the brain he was given. Hope that makes sense.
I realize, and he will eventually, that if he stays in the Navy he will be a leader, maybe sooner than later. It's just that I read posts here from parents/kids whose goal is to become an officer. Well, that's not my son's goal. I'm going to show him these posts, I think the one that said he WILL end up being a leader will open his eyes a bit. Hopefully he will like what he sees.
The post with the practical advice was very helpful. It's all stuff we work on, but admittedly we're going to have to speed up the process a bit. Our other two kids stayed at home during their first 2 yrs of college, so we could help them step by step.
He's finding out the more people that find out about his plans, the more people there are to talk to. We live about 10 miles from DavisBesse so there are lots of retirees and folks still employed there. Everyone seems to know someone who works there, and most of them seem to have been in the Navy. I even called them and talked to the HR gal about employment opportunities, requirements. She said they are looking for operators now, and someone with 4 yrs in the military with nuke experience would be qualified. By the end of the first year, they are making almost as much as my husband does out at the refinery. We've always felt it's our job to send the kids off with the ability to take care of themselves, not the ability to be millioniares. That they have to do themselves.
Obviously we are a blue collar family, so our son has seen what can be gained from hard work. We'll see how far that takes him.
He's still in DEP so we have a while before he leaves. I know it will go by much too quickly.
I have a feeling he will be here reading when he gets the opportunity, thanks for taking the time to help us, both here and in private.