[h4b4n3r0]

You will still benefit from your past experience. Novices don't know what to pursue, so they waste a lot of time. You're past that, you have the luxury of just knowing which fluff to ignore.

As to how to get back into it: it's the same way as you get into any other non-trivial field. Starts working on a small but concrete problem, and then just build from there. That's the only way to accomplish anything non-trivial.