The military is a serious commitment. Unlike trying a job out, you can't quit if you don't like it without serious results.
Try votech, try college, try wleding, try lots of things and work hard at them and see what you like. While it is commendable to be so serious about your future, you've got a lot of time ahead to narrow your field, to find out what really floats your boat.
As to your weight, if you can focus the same seriousness that you are considering your future to changing you body to the best it can be, not some image that the media presents, you'll do fine. Get a good physical, ask the doctor, have your bodyfat calculated, eat the best you can.
And watch out for those recruiters, they are salesmen.
Good luck and keep us posted.