Well I suppose it's hard to say.. Boxing is boxing in a way... You can start off getting fit. No matter WHEN you start going to a gym and training, you'll alwayssss need fitness. In the first few months of training, the fitness is a LOT harder to get through than actually learning the skills.
So start going for short runs and turn them into long runs. Get a skipping rope. You can get one for $5 and it'll do just as good job as any,, and start using it. All this will pay of in the future without a doubt.
Depending on what your gym/trainer is like, I suppose that's what will decide how far you get 'thrown into' boxing. You may get a trainer that realy just focuses on fitness first and then goes over the basics a lot of the time, getting them perfect. You may get a trainer who wants to get you in sparring as soon as possible. It all depends.
Do you have a gym or trainer? If their is one in your area, just go and watch a session or better yet, go in and sign up for a class. Their is absolutely no replacement/substitute for going to a trainer and doing a class. So yeah, I think how your asking it, you should just throw yourself in their if the opportunity is there. But if you're looking for where to first get started, start working on your fitness a little.
Their are a few tutorials on here about your stance and the basic punches & it absolutely won't hurt to read up as much about them as you can and even start practicing. Knowing the basics always helps when you join a class, and as long as you've done your best to use the technique described as best you can, your trainer should be able to help you fine tune your form and what your doing wrong..

It's really up to you where you start, but signing up for a class is about 20 levels ahead of just about any other place you could start.

Once you get going, their are a lot of people on here that will answer anyyyy question you might have!