Doug,
at 23 years old you are very hard to employ as an apprentice. 95% of prospective employers will shy away from you simply based on your age, and the life experiences that have set you in your ways. That is not to say you can't be taught, but its a common held viewpoint on civvy street.
There are 2 types of employer of apprentices.
Type 1 see's a first year as cheap labour...teaching them is optional.
Type 2, see's an apprentice as a potential asset who won't make them any money until late in their 2nd year, but makes the investment.
At your age, only a type 2 employer would consider employing you, and they are few and far between, across ALL industries.
My advice to you, is to stay in the army and apply to learn the trade there. It won't do you any harm, because you will receive the best training available.
If the army won't train you, think about an interservice transfer to take up what you want to do.
I looked at it years ago, during the recession we had to have....join the army as a grunt and then apply for other stuff once in. You are in...use it wisely chum.
Cheers
Jas
ps..goodluck